Maybe my first serious post, don't judge me.
I like Luffy vs Kaido because it brings the Manga to its roots, when One Piece didn't take itself too seriously. I always disliked Dressrosa because of Doflamingo.
This type of panel did nothing for me. I remember back in the day everybody was wetting their panties in forums about how badass and dark Doflamingo is but to me it was just edgy and cringe.
What made me fall in love with Luffy's character were arcs like Arabasta, Skypiea and Arlong Park, where Oda cleverly built up the villains through the eyes of their victims, so they always seemed terrifying to us, but then radically changed the tone when Luffy met them face to face.
Take Arlong, he comes from the superior race originating from the Grand Line. At first, the Mugiwaras are dicking around in Kokoyashi without a worry. Oda hypes up Arlong up in our imaginations by showing his underlings sinking Marine ships effortlessly, by showing Arlong terrorizing Usopp and lifting houses (it's more terrifying if it's Usopp), we hear about how Fishmen are 10 times stronger than humans, Arlong's shark teeth etc.
Then as the arc developped it starts becoming personal. Arlong's invincibility aura grows more in Nami's flashback, but so does his ruthlessness as he murders Bellemere and enslaves the entire village.
Through this build-up we take this villain super seriously, we fear for Luffy. And this is why I think One Piece managed to conquer the hearts of children, teenagers and adults all over the world; After so many chapters of people jobbing to Arlong, being terrified of Arlong, etc., Luffy finally meets Arlong face to face and he doesn't care.
He isn't scared, he doesn't respect him, he goofs around and mocks him. Arlong is just some dude to him. Oda builds all this illusion of the invincible foe through the perspective of powerless people, but when Luffy gets there, this illusion is shattered.
Luffy's character was too fucking cool. No matter how serious the situation was, he would make us laugh and never changed his relaxed/carefree attitude. Enel, the omnipotent God who was one-shotting everybody in Skypiea, looked silly trying to stab Luffy's Gomu Gomu no Baka.
tl;dr: One Piece is different from edgelord shit like Bleach (if you are a Bleach fan put your money where your mouth is and drink Bleach please) because it doesn't take itself too seriously. Oda manipulates the readers into hyping up the antagonist in their imaginations, only to have Luffy reminds us that they're just human.