Let's see, Loki, Vulture, Killmonger, Thanos... I figure everyone would agree on those being the best. Oh and Green Goblin, Willem Dafoe truly made that character his own in No Way Home.
Personally I also loved Justin Hammer and wish he'd come back. Scarlet Witch as a villain was fun, but coulda used a bit more buildup.
I was actually hyped for Kang until... well the drama happened.
Sad that they completely backtracked on how they handle villains. That Ronan cosplayer from the Marvels was embarrassing.
I don't kill... but I don't lose either.