Try saying The Big Ticking Time Bomb Big Mom five times fast (insert San's laugh here).
TLDR: We have rarely seen Big Mom at her strongest. Big Mom is most powerful when she's hungry, as seen in her Elbaf flashback and Whole Cake Island when she didn't get her cake and started losing weight.
Big Mom has been in the bottom of Wano's magma pools for around two weeks. When she comes out, THINGS ARE GOING TO GET VERY BAD VERY FAST
Stick around to the end for the special "Big Mom eats Kaido" section
Real ones know this big beautiful women isn't dead. A few reasons for the doubters:
1. Top tiers/important characters have dramatic deaths that actually show them dying, or prove they're totally dead, even if the corpse isn't shown: Roger, Oden, Noland, Whitebeard, Ace, Pedro, etc.
2. As long as she's not in the weird vulnerable state, she's more or less invulnerable to anything that isn't Haki or internal attacks
3. Oda didn't kill a Yonkou with rando bombs, LOL, come on, just stop it
4. Elbaf exists and Big Mom has been tied to it enough times to prove Elbaf is a part of her narrative that needs to be resolved
You can argue that Zeus's continued existence proves Linlin is still alive, too, but, I think Zeus might have been detached from Big Mom's Soul in his "fight" with her, so, I'm not sure about that as evidence.
Point being, people just hate Big Mom, and don't want her to come back. But, the only thing that can keep a Big Mom down is gravity (and even that's debatable since she literally walked out of the earth in Whole Cake).
Big Mom on Whole Cake became insanely powerful the hungrier she got after being denied her Wedding Cake. Becoming faster, and possibly stronger, she went from the normal crazy old granny, to a shrieking flaming banshee of an old hag.
This seems to be a special state driven purely by hunger; as far as we know, during her long duel with Kaido, she suffered no such hunger attacks. So, in order for Big Mom to go into this special state, the requirement is simple:
Being denied food she intensely craves.
O-SHI-RU-KO!!!
Once Big Mom enters her Hunger Form (what I'm calling it), she begins to burn calories at a RAPID rate, which is what increases her speed, but also leaves her more vulnerable. So, it works like this:
Big Mom while happy and full = Much more endurance and defense,
Big Mom while in Hunger Form = More speed, more desire/Will, more raw power
Big Mom is essentially doing what Luffy does with his blood-doping through Gear 2 when he increases his blood flow to strengthen himself; she's rapidly increasing her metalobic rate in order to burn through her fat to gain greater power. She loses her natural endurance due to reducing the fat that shields her organs, bones, and musclular tissue, and is on a timer, but becomes much stronger, like Luffy.
But, when we saw Big Mom in Hunger Form in Whole Cake, she had been well fed prior, and was only chasing the Straw Hats for a few fours. And, look at how much weight she lost, and how insane she became.
What's the point of all this?
We have never seen Big Mom's full potential as she currently is.
So, what's she been doing? Oh, just starving for nearly two weeks. Sitting in magma, craving Oshiruko. But, CoC, you say, how will Big Mom get out? What could free her? Well, if she's trapped in magma, or volcanic rock that hardened from sea water hitting the lava, would an earthquake help?
Oh, Imu, you silly goose; you just blew up some rando island, and, in doing so, let loose a screaming, raving, hungry demon onto Wano. And Kaido.
Speaking of Kaido:
One of the biggest Chekov's guns in One Piece at the moment (outside of fucking Pluton god damn it Oda) is Kaido's debt to Linlin. Oda has brought this up MULTIPLE times, and made it clear that it's a big deal to Big Mom.
What's the easiest way to repay a straving woman trapped in magma? Feed her. Yourself. Feed her, yourself. Feed her yourself. Let Big Mom eat a limb. Think this is a random theory? Ohhhhhh, did Oda foreskin this happening a long time ago (yes, the typo was intentional because I am a goof).
Big Mom is an antithesis to Zeff, which is why she was the Big Bad in Sanji's big backstory arc. Look at their characters, Big Mom and Zeff are dark mirrors of each other:
Zeff is a cranky asshole whole openly berates everyone around him. He adopted a single kid, Sanji, who he acts like he hates, but really loves. Zeff ate his own leg to save Sanji, and then wanted him to leave to become his own person and chase his dream. Zeff desires to feed hungry people, even if they have nothing, and hates wasting food. Zeff gave up Piracy for his adopted child.
Big Mom has her own giant family, and acts like a nice, kind person, but is really cruel and manipulative. She is willing to destroy her own children while hungry, wastes food if it doesn't suit her, and forces her own children to remain in her crew to serve her dream, hating them if they leave. Big Mom orders people to give her food, and will steal it from them or destroy them, even if they have nothing. Big Mom uses her own children to commit global crimes of Piracy.
Zeff ate his own leg in order to survive, so Sanji, a younger person with the same dream, could survive. SO, Big Mom's twist here would be... eating someone who owes her something.
Kaido will feed his own limb to Big Mom, in order to pay off his debt from God Valley and keep her from dying from starvation.
Because, Kaido is the dark mirror of Sanji in this situation: Kaido is an orphan (just like Sanji), who is a genetic anomaly a country wanted to use for war (just like Sanji), who got arrested by the Marines in order to eat (Sanji was saved by a pirate who starved himself). Kaido was mentored by an older pirate (just like Sanji), who he owes a life debt to (just like Sanji), who he had to leave after a huge fight involving pirates (just like Sanji). Kaido came from a war-torn country; Sanji's family, the Vinsmokes, take advantage of war torn countries. Kaido lets people be genetically manipulated through SMILES; Sanji was genetically manipulated and hates it. Kaido fled his home because he was too powerful; Sanji was kicked out of his home because he was too weak.
Big Mom is obsessed with food, and her country is LITERALLY MADE OF FOOD, while Kaido has been starving a nation and destroying its crops and poisoning its water supplies for fucking 20 years. SANJI IS THE BRIDGE BETWEEN THESE TWO ARCS. Sanji fed Luffy when he was starving, after abandoning him.
How did Kaido react to Big Mom losing?
Kaido immediately remembers how Linlin helped him in the past, and was a mentor to him. Then, he shouts, "How could I let this happen?!? WE just swore that WE'D help each other get the One Piece!"
This is drunk ass Kaido (no seriously, I know because this is how I get when I'm drunk), he's baring his open feelings. This isn't a lie or trick. KAIDO IS MISERABLE at his failure. The Strongest Creature in the World, and he couldn't even protect another Yonkou. Kaido feels GUILT over this. Deep down, he truly cares about Big Mom, about Charlotte Linlin, as Nakama, as his mentor.
Kaido got what he wanted, besides an honorable death; he was defeated by Joy Boy, the man he wanted to beat him.
Now, he will let Big Mom continue on, by feeding her his body (I'm guessing an arm). Kaido returns to his roots: like Shanks giving up his arm for the younger generation, Kaido will give up his arm to the woman who molded him into a Yonkou in the first place.
Zoro will still kill Kaido, later, though, don't worry!
Big Mom Eats Kaido, BMEK. MMMMMM MMMMMMM MMMMMMMMMMMMMMMMM. Deep fried dragon, delicious!
I also hope we see Kaido trying to contain crazy, hunger pains Linlin, so we can get a serious Kaido vs Big Mom fight.
Poor dude is going to feed this crazy old lady his arm, and she'll still just want Oshiruko and go on a rampage for it. Pregnant women, amirite? /s
TLDR: We have rarely seen Big Mom at her strongest. Big Mom is most powerful when she's hungry, as seen in her Elbaf flashback and Whole Cake Island when she didn't get her cake and started losing weight.
Big Mom has been in the bottom of Wano's magma pools for around two weeks. When she comes out, THINGS ARE GOING TO GET VERY BAD VERY FAST
Stick around to the end for the special "Big Mom eats Kaido" section
Big Mom doesn't die: SHE FUCKS
Real ones know this big beautiful women isn't dead. A few reasons for the doubters:
1. Top tiers/important characters have dramatic deaths that actually show them dying, or prove they're totally dead, even if the corpse isn't shown: Roger, Oden, Noland, Whitebeard, Ace, Pedro, etc.
2. As long as she's not in the weird vulnerable state, she's more or less invulnerable to anything that isn't Haki or internal attacks
3. Oda didn't kill a Yonkou with rando bombs, LOL, come on, just stop it
4. Elbaf exists and Big Mom has been tied to it enough times to prove Elbaf is a part of her narrative that needs to be resolved
You can argue that Zeus's continued existence proves Linlin is still alive, too, but, I think Zeus might have been detached from Big Mom's Soul in his "fight" with her, so, I'm not sure about that as evidence.
Point being, people just hate Big Mom, and don't want her to come back. But, the only thing that can keep a Big Mom down is gravity (and even that's debatable since she literally walked out of the earth in Whole Cake).
The Starving Beast Emerges
Big Mom couldn't handle eating without a week AS A CHILD, and, after failing to hold out on her fast on Elbaf, she destroyed a village and murdered an elder Giant, Jorul, in one blow. THIS WAS CHILD BIG MOM. 
Big Mom on Whole Cake became insanely powerful the hungrier she got after being denied her Wedding Cake. Becoming faster, and possibly stronger, she went from the normal crazy old granny, to a shrieking flaming banshee of an old hag.
This seems to be a special state driven purely by hunger; as far as we know, during her long duel with Kaido, she suffered no such hunger attacks. So, in order for Big Mom to go into this special state, the requirement is simple:
Being denied food she intensely craves.
O-SHI-RU-KO!!!
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Once Big Mom enters her Hunger Form (what I'm calling it), she begins to burn calories at a RAPID rate, which is what increases her speed, but also leaves her more vulnerable. So, it works like this:
Big Mom while happy and full = Much more endurance and defense,
Big Mom while in Hunger Form = More speed, more desire/Will, more raw power
Big Mom is essentially doing what Luffy does with his blood-doping through Gear 2 when he increases his blood flow to strengthen himself; she's rapidly increasing her metalobic rate in order to burn through her fat to gain greater power. She loses her natural endurance due to reducing the fat that shields her organs, bones, and musclular tissue, and is on a timer, but becomes much stronger, like Luffy.
But, when we saw Big Mom in Hunger Form in Whole Cake, she had been well fed prior, and was only chasing the Straw Hats for a few fours. And, look at how much weight she lost, and how insane she became.
What's the point of all this?
We have never seen Big Mom's full potential as she currently is.
So, what's she been doing? Oh, just starving for nearly two weeks. Sitting in magma, craving Oshiruko. But, CoC, you say, how will Big Mom get out? What could free her? Well, if she's trapped in magma, or volcanic rock that hardened from sea water hitting the lava, would an earthquake help?

Oh, Imu, you silly goose; you just blew up some rando island, and, in doing so, let loose a screaming, raving, hungry demon onto Wano. And Kaido.
Speaking of Kaido:
Bonus Clown Content: Big Mom Eats Wano-Kuni Fried Kaido
One of the biggest Chekov's guns in One Piece at the moment (outside of fucking Pluton god damn it Oda) is Kaido's debt to Linlin. Oda has brought this up MULTIPLE times, and made it clear that it's a big deal to Big Mom.
What's the easiest way to repay a straving woman trapped in magma? Feed her. Yourself. Feed her, yourself. Feed her yourself. Let Big Mom eat a limb. Think this is a random theory? Ohhhhhh, did Oda foreskin this happening a long time ago (yes, the typo was intentional because I am a goof).
Big Mom is an antithesis to Zeff, which is why she was the Big Bad in Sanji's big backstory arc. Look at their characters, Big Mom and Zeff are dark mirrors of each other:
Zeff is a cranky asshole whole openly berates everyone around him. He adopted a single kid, Sanji, who he acts like he hates, but really loves. Zeff ate his own leg to save Sanji, and then wanted him to leave to become his own person and chase his dream. Zeff desires to feed hungry people, even if they have nothing, and hates wasting food. Zeff gave up Piracy for his adopted child.
Big Mom has her own giant family, and acts like a nice, kind person, but is really cruel and manipulative. She is willing to destroy her own children while hungry, wastes food if it doesn't suit her, and forces her own children to remain in her crew to serve her dream, hating them if they leave. Big Mom orders people to give her food, and will steal it from them or destroy them, even if they have nothing. Big Mom uses her own children to commit global crimes of Piracy.
Zeff ate his own leg in order to survive, so Sanji, a younger person with the same dream, could survive. SO, Big Mom's twist here would be... eating someone who owes her something.
Kaido will feed his own limb to Big Mom, in order to pay off his debt from God Valley and keep her from dying from starvation.
Because, Kaido is the dark mirror of Sanji in this situation: Kaido is an orphan (just like Sanji), who is a genetic anomaly a country wanted to use for war (just like Sanji), who got arrested by the Marines in order to eat (Sanji was saved by a pirate who starved himself). Kaido was mentored by an older pirate (just like Sanji), who he owes a life debt to (just like Sanji), who he had to leave after a huge fight involving pirates (just like Sanji). Kaido came from a war-torn country; Sanji's family, the Vinsmokes, take advantage of war torn countries. Kaido lets people be genetically manipulated through SMILES; Sanji was genetically manipulated and hates it. Kaido fled his home because he was too powerful; Sanji was kicked out of his home because he was too weak.
Big Mom is obsessed with food, and her country is LITERALLY MADE OF FOOD, while Kaido has been starving a nation and destroying its crops and poisoning its water supplies for fucking 20 years. SANJI IS THE BRIDGE BETWEEN THESE TWO ARCS. Sanji fed Luffy when he was starving, after abandoning him.
How did Kaido react to Big Mom losing?

Kaido immediately remembers how Linlin helped him in the past, and was a mentor to him. Then, he shouts, "How could I let this happen?!? WE just swore that WE'D help each other get the One Piece!"
This is drunk ass Kaido (no seriously, I know because this is how I get when I'm drunk), he's baring his open feelings. This isn't a lie or trick. KAIDO IS MISERABLE at his failure. The Strongest Creature in the World, and he couldn't even protect another Yonkou. Kaido feels GUILT over this. Deep down, he truly cares about Big Mom, about Charlotte Linlin, as Nakama, as his mentor.
Kaido got what he wanted, besides an honorable death; he was defeated by Joy Boy, the man he wanted to beat him.
Now, he will let Big Mom continue on, by feeding her his body (I'm guessing an arm). Kaido returns to his roots: like Shanks giving up his arm for the younger generation, Kaido will give up his arm to the woman who molded him into a Yonkou in the first place.
Zoro will still kill Kaido, later, though, don't worry!
Big Mom Eats Kaido, BMEK. MMMMMM MMMMMMM MMMMMMMMMMMMMMMMM. Deep fried dragon, delicious!
I also hope we see Kaido trying to contain crazy, hunger pains Linlin, so we can get a serious Kaido vs Big Mom fight.
Poor dude is going to feed this crazy old lady his arm, and she'll still just want Oshiruko and go on a rampage for it. Pregnant women, amirite? /s