Whoever wrote The Crossing is the Avengers biggest adversary, but if we’re talking villains I’d say Kang or Ultron. Personal favorite is Gravitron or Morgan Le Fey.
Baron Helmut Zemo and/or the Masters of Evil
Count Nefaria
Dormammu
Grandmaster
Immortus
Kang the Conqueror
Kree Empire
Loki
Michael Korvac
Scarlet Witch
Skrull Empire
Squadron Supreme
Thanos
Ultron
Zeus
Whoever wrote The Crossing is the Avengers biggest adversary, but if we’re talking villains I’d say Kang or Ultron. Personal favorite is Gravitron or Morgan Le Fey.