MickeyAdaptus

Perturabo: Fist me, Rogal!

Rogal Dorn: Yes.....

But being real here, those 2 legions have a bigger grudge then just the usual traitor legion trend going on, after the iron cage, you can see just how big of enemies they are.

Yep though I think you can say the same about perterabo and fulgrim after the angels exterminatus incident 

Ah yeah, that also, Fulgrim really backstabbed him there.

I think the biggest one to this day will be the burning of Prospero for my oppinion. You can see the sheer hatred between Leman Russ and Magnus the Red, especially after the siege of Fenris.

And then comes the fact that those are still both alive (Leman Russ presumed lost in the warp after his journey into the Eye of Terror, looking for the tree of life that comes from Fenrisian legends, in perhaps being able to resurrect/heal the Emperor.)