While Askeladd isn't technically a villain, he is the antagonist for quite a lot of the show, and i think that combined with his contribution to the story is what really sets him apart from what we know as an antagonist. He reminds people that not all antagonists are villains and can be the star.

Askeladd is easily one of the best anime antagonists among dio, frieza, madara, doffy etc.

Has beard.

It's not even his character that I'm voting for its what he does for the protagonist Thorfinn