Which is the X-Men's biggest foe they've never fought alongside?

[Senyaka]

I was thinking around the X-men "morally grey" trope where they have worked alongside most of their villains and it got me thinking - which is the biggest villain that even they haven't fought on the same side as?

Apocalypse - worked with the X-men & the FF to try and destroy Onslaught
Mystique - Was on Rogue's X-men despite every single character saying she would betray her (spoiler alert - she betrays her)
Sentinels - not counting Omega Sentinel there have been several classic robots working with them
Sinister - pretty sure he was a kind of ally of X-man
Magneto - not even worth mentioning goes back and forth so often.

Best I can think of is Cassandra Nova and that's only because the timeline when she was an X-men ally was prevented by Jean Grey

So what say you? both alternate universe and 616 only - am almost positive any character with multiple appearances was an ally in some universe.

[WallStreeter]

I was thinking around the X-men "morally grey" trope where they have worked alongside most of their villains and it got me thinking - which is the biggest villain that even they haven't fought on the same side as?

Apocalypse - worked with the X-men & the FF to try and destroy Onslaught
Mystique - Was on Rogue's X-men despite every single character saying she would betray her (spoiler alert - she betrays her)
Sentinels - not counting Omega Sentinel there have been several classic robots working with them
Sinister - pretty sure he was a kind of ally of X-man
Magneto - not even worth mentioning goes back and forth so often.

Best I can think of is Cassandra Nova and that's only because the timeline when she was an X-men ally was prevented by Jean Grey

So what say you? both alternate universe and 616 only - am almost positive any character with multiple appearances was an ally in some universe.

They never fought on the same side as some of their magical enemies like the N'Gari, Belasco, and the Adversary. They never fought on the same side as the Dire Wraith's or the Brood.

[Senyaka]

Was there not a rogue N'gari in the 90s called Pilgrim who worked with them? On the same theme Broo definitely counts as a Brood on their side.

Belasco I may give you, but honestly cant remember seeing him since early Claremont so not sure if he can be classed as "big".

[nx01a]

I'd say Selene.
Special mention to S'ym and N'astirh.

[Arya]

Shadow King comes to mind.

[Darth Phoenix]

I'd say Selene..

Selene was part of the Hellfire club when Storm/Mags joined them to the Xmen.
The xmen and Hellfire Club(Selene was Black Queen then) teamed up to fight Nimrod before that as well.

[Darth Phoenix]

Emplate,the Reavers,MLF, are team up free I think

[Senyaka]

Emplate,the Reavers,MLF, are team up free I think

Sage forced Pretty boy the Reaver to turn and fight with the X-Men against the rest of them I think I recall in X-treme x-men.

Plus almost certain Lady Deathstrike reluctantly worked with the X-Men a few times, although can't remember details.

[Darth Phoenix]

Sage forced Pretty boy the Reaver to turn and fight with the X-Men against the rest of them I think I recall in X-treme x-men.

Plus almost certain Lady Deathstrike reluctantly worked with the X-Men a few times, although can't remember details.

Thanks for point out

[Senyaka]

Thanks for point out

No worries, thanks for the input!

I'd say Emplate or Shadow King winning right now.

[dragonmp93]

I think that Madelyne Pryor.

[Limerick]

They never fought on the same side as some of their magical enemies like the N'Gari, Belasco, and the Adversary. They never fought on the same side as the Dire Wraith's or the Brood.

Wasn't there a Brood kid in the Wolverine school post Schism?

[Limerick]

Wasn't there a Brood kid in the Wolverine school post Schism?

Oh yeah,somebody already got there

[Limerick]

I'd say Selene.
Special mention to S'ym and N'astirh.

S'ym was loyal to Magik(mostly) in his pre-Inferno appearances and worked alongside the New Mutants a little,IIRC.

[Goddess]

I'd say Selene.
Special mention to S'ym and N'astirh.

Yup. Selene and Shadow King. Pure evil characters.