Kaido would be a threat to Wano and Luffy, even after he becomes a pirate king. He is a monster with extraordinary strength. Also, his dream is to start a world war and enslave people, unlike Big Mom who just wants to have a tea party and gather all races.
When will these people understand that he is too dangerous to be kept alive in the story....my god smh
Somebody gonna kill Kaido in this arc and Zoro is the top contender to do it.