Wolverine --> Sabretooth
Rogue & Gambit --> Bella Donna
Psylocke --> Mojo and Shadow King
Archangel --> Apocalypse
Moonstar --> Deamon Bear
Magik --> Belasco
Xavier--> Proteus and Shadow King
Cyclops --> Sinister
Wolverine --> Sabretooth
Rogue & Gambit --> Bella Donna
Psylocke --> Mojo and Shadow King
Archangel --> Apocalypse
Moonstar --> Deamon Bear
Magik --> Belasco
Xavier--> Proteus and Shadow King
Cyclops --> Sinister
"COURAGE, DON'T YOU DARE LET ME DOWN"
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Havok - - > The Living Monolith
Magik - Belasco plus any named Limbo demon like S'ym and N'astirh. Maybe Witchfire. While they will appear as villains for the entire X-Men, their relationship and history with Illyana will always be at the forefront even if she's not around. The World Eater from the Lemire run is 100% exclusive to her.
Mr. Sinister is similar for Cyclops. That's what he'll be identified as even if his plans have nothing to do with Cyclops this time.
Wolverine has Sabertooth, Omega Red, and Silver Samurai.
Moonstar - Demon Bear.
Wolfsbane - Reverend Craig.
Shadow King should be Karma's villain and Selene should be Magma's villain given the Fat Karma and Nova Roma stories, but neither really seems to be the case.
Bishop - Trevor Fitzroy. Not that he's used much but aside from his intro story I don't think he bothered the X-Men too much.