aizen by far is the better villain. the moment he revealed himself as one was monumental in the show and outside it considering no one in the slightest even thought aizen was the villain. his plan was eh a little off but thats about it. yhwachs villain reveal was surprising but kinda expected.
Aizen is the better villain. Dude’s introduction as a villain was so unexpected and he quickly proved himself to be extremly dangerous. Also, 2 of the 3 most bad ass moment of Bleach was Aizen bodying the Gotei as they helplessly fell from the sky while he smiled and him challenging Yhwach in the end.
That said, his character temporarily became trash after he fused with Hogyoku, idk he kinda lost his charm, good thing he got it back in TYBW.