Worstgen
Bisoromi Bear
The Shichibukai
Light D Lamperouge
The Akatsuki(Naruto), The Phantom Troupe(HxH), The Port Mafia(BSD), The Homunculi(FMA), The Noah Clan(DGM). Off the top of my head. I personally like the Espada too as well as some Upper Moons.
Rej
you consider the Port Mafia villains? interesting, I see it a bit different
Light D Lamperouge
@Rej honestly all groups above bar maybe the Homunculi aren't really straight up evil and stuff or not all of their members are like that. But they are at odds with the protagonist and his side so they're classified as villain groups imo. How do you see it?