I posted this list in a previous thread:

Starting roster:
Wolverine
Thor
Venom
Psylocke
Black Panther
Doctor Octopus
Thanos
Rocket
Carol (though I have reasons to doubt it)
Dr. Strange
MODOK
Magneto
Electro
Hulk
Ant-Man
Gamora
Silver Samurai
Jean Grey

Then for DLC:
Green Goblin
Deadpool
Sandman
Scarlet Witch
Jubilee
Mysterio

And guest characters if even allowed:
Deku
Spawn
The Mask
Ninja Turtles
Invincible
Jotaro Kujo