Personality: Kaido is an inconsistent mess who's only consistency is how inconsistent he is. On the one hand, he is screaming at his men to stop Big Mom from entering Wano at all costs, and the next he is demanding they remove her seastone cuffs so that he can kill her in a fair 1v1 fight himself (like wut?). 795 Kaido was eager for death and actively sought ways to kill himself for fun, but Wano Kaido shits himself at the very idea of experiencing pain in any form and very much does not seem like he wants to die at all. Kaido claims that he wants to go to war with the entire World Government and Wano, but visibly shits himself at the very idea of Oden's scabbards picking a fight with him. Kaido spends 50% of his panel time being drunk, which gives him an even
more inconsistent personality on top of how messily inconsistent his character is already. He is someone who is both terrified of a good fight, while also spending his life seeking out the largest scale war imaginable.
This character is one of the shittiest I've ever seen in terms of his personality, and there is nothing to like about him whatsoever because his personality changes into its polar opposite form every other panel.
How would I change this? Consistency is a start. Either Kaido needs to be a fearless Warmonger who eagerly fights Big Mom as soon as she enters Wano instead of begging his subordinates to protect him, or he needs to be a consistent coward who doesn't take Big Mom's handcuffs off because he's terrified at the idea of fighting her. Kaido should not fear pain, he should actively seek out opportunities to die as he was introduced. His first action when he saw Big Mom, should've been to present his neck to her in hopes that she could actually behead him and end his boring existence. Once she fails, then that should be when Kaido fights her himself because that would fit his adrenaline-seeking nature that exists half of the time.
Drunkenness is not an excuse for shit-tier consistency. Drunkenness should amplify Kaido's most extreme traits, not remove them entirely for the sake of gags. Drunken Kaido should be
even more eager for a fight. He should be
even more violent and impulsive. He shouldn't be shitting his pants at the idea of fighting the scabbards if his actual goal is to start a war on the largest possible scale. Being drunk is when people reveal who they truly are, and by drawing Kaido as a coward when he's drunk, the message Oda is sending is that Kaido is actually a coward deep down, and him starting a war with the entire World is just a sober facade. Which, of course, makes absolutely no sense unless of course Oda truly does want us to see Kaido as a coward instead of the adrenaline-junky-war-monger that Kaido was introduced as.
There are many more changes I would make but these are just some examples.
Motivations: Kaido's motivations are literally as generic as they get, on the rare occasion that he actually decides to show a consistent motivation and character. Kaido's motivation, is that he wants to destroy the world. I wish I was making that up because it's a simplistic motivation even for children's stories and far too simple for a story as nuanced as One Piece, but Oda really thought that the Arc he's been hyping for 8 years needed a villain with literally the most generic and forgettable possible motivation.
How would I change this: If you're going to give Kaido the most generic and un-nuanced motivation possible, there at least needs to be an understandable, rational backstory that justifies this. How about making Kaido the opposite to Oden? Oden travels the world and sees it's beauty and thus wants to open the borders to Wano to let the "beauty" in, but Kaido travels the world and sees how terrible it is (getting captured, death sentences, etc) and so he resolves to destroy the world and keep the borders to Wano shut so all of the "evil" can't get in. This may be what Oda is going for but we haven't gotten to Kaido's backstory yet because Oda is interested in far more...."important" plotlines like how Kinemon found the baby pig, Oden dancing throughout the streets of Wano for no reason whatsoever, Big Mom's makeup getting ruined via a face-fucking by a motorcycle, etc.
Design: Kaido's design is lazy, uninspired, and has nothing to do with his character (it's hard to make a design that contributes to your character when you have no character whatsoever so I get it). Let's use Doflamingo for example:
Doflamingo's design is meant to exemplify his flamboyant personality, which is a result of his World Noble upbringing which leads him to believe that he is superior to everyone else. He wears an extravagant feather coat which simultaneously shows his self-assurance and charisma while also emphasizing the riches he has earned from his underworld business. His manipulative personality is also complemented by his manipulative Devil Fruit which literally lets him turn people into his puppets, and his Devil Fruit also contributes to his secondary "spider" theme, as Oda gives Doflamingo both primary and secondary animal themes which emphasizes his "hidden" nature to the rest of the world. Doflamingo's primary animal theme being the Flamingo (emphasizing his extravagance and flamboyance) and his perception to the people of Dressrosa was that of a loving king, but his secondary and more hidden theme is the Spider (which emphasizes his manipulative, blood-sucking character) with his true nature being that of a psychotic manipulator.
Doflamingo's design contributes to his character in every way, and his Devil Fruit, Personality, and Design have been made in conjunction with one another to illustrate who Doflamingo is on several metaphorical levels. Doflamingo is
not the only character Oda does this with, but he is a nice quick example.
Now let's look at Kaido's design.
Okay so...I'm not even sure what Kaido's design even is first of all. Doflamingo is meant to look like an extremely successful drug-dealer, which is basically what he is in One Piece lol. Kaido is meant to look like...a big muscular man? I mean seriously, wtf even is he? And how does his design contribute to his character?
The rope Kaido is wearing around his waste is called a "Makuuchi" which is apparently a belt worn in Sumo Culture, which has nothing to do with Kaido or his established character so far. A Makuuchi can also be used to symbolize a "sacred" object, but again this has had no relevance to Kaido so far. Kaido is also wearing a shide which is used in Shinto rituals which...I won't go into here, but based on my research, again this has nothing whatsoever to do with Kaido, other than the fact that Kaido has an attack named "Divine Thunder" for what thus far appears to be no reason whatsoever. Again, compare this to Doflamingo who is wearing a stylish button-up shirt meant to emphasize his stylish personality, unbuttoned to show his charisma. See how Doffy's design contributes to his character and Kaido's doesn't?
Kaido's Dragon Devil Fruit (presumably) serves the purpose of emphasizing...what aspects of Kaido's personality exactly? Dragons in mythology are meant to be wise, immortal beings. Kaido might be immortal, but he is far from wise, being consistently out-smarted and having spent his entire life pretty much failing at every serious goal he's ever attempted. He's got a skull tattoo which emphasizes that he wants to die but...again like I mentioned above, he only wanted to die in Chapter 795 and we've never seen this aspect of his personality on display ever again. A Immortal Dragon who wants to die would actually be an interesting concept, which makes Kaido even shittier since this aspect of his personality seems to have been retconned into non-existence.
I'm so at a loss for words to explain what Kaido is even supposed to be, what aspects of his personality and character his design is meant to emphasize, and how his Devil Fruit is supposed to tie into all that that I really don't even know what to say. His design, is truly awful. And I mean that genuinely. Oda should be ashamed of himself on this one. Sure we don't know Kaido's exact backstory yet, but literally every minor detail we learned about Doflamingo, and it became clearer and clearer why Oda designed him the way he did and what the aspects of his design are supposed to represent. With Kaido, Wano is like 100 chapters now and we still have no idea who or what he is or how his design contributes to that.
How would I change this: Well, Kaido's design needs to better emphasize his personality and overall character, so his these things needs to be fixed before his design can. His Devil Fruit also needs to factor more into his personality more, and there are several ways to do this.
I love the idea in my head of Kaido being a Chopper-esque character, in that he's literally a Dragon who ate the Human Human Fruit (Mythical Model: Oni) which would both explain Kaido's immortality as well as explain why he's referenced as a creature and not as a human. I don't want to delve too deep into how I would fix this without fully knowing what Oda intends for Kaido and his backstory, I don't want to "fix" something that might not even be broken at all, but it's hard for me to imagine Oda salvaging this shitshow.
Some quick fixes: Get rid of the Makuuchi, or make sumo more relevant to Kaido's character right from the start. Make it more obvious why Kaido is supposed to be considered "sacred" (does Wano culture consider Dragon's sacred? Is Kaido the last Dragon which makes the people of Wano worship him? Religion has literally had nothing to do with Kaido and his character 100 chapters into Wano). Incorporate real aspects of Shinto-ism into Kaido's personality and actions, thus justifying the Shide that he is wearing.
Imagine Franky hitting Mihawk instead of Big Mom, would he survive? 
Big Mom's skin is extremely tough and Mihawk doesn't have that 
it was all downhill after that. Maybe the problem with her is her own strength. Oda made her so damn OP that he needs an excuse to keep her on check. He never should have brought her to Wano so early if he was just going to make more Big Meme out of her. Maybe the final war of Wano demands it but he could have just added Big Mom somewhere in between and not at the beginning of the arc.
