This is always up for debate but now we are beginning to see them in the game it will be interesting to see how they handle it
The few facts we have of combat between them follows
Horus kills the angel
Corax beats up logar
Corax avoids the night hunter, doesn't think he can beat him
The lion almost kills cruze (but cruze gets better, second fight cruze legs it)
Fulgrim kills manus
Russ cripples Magnus and kills the other 2
The lion beats Russ who then keeps fighting and beats up the lion (problerly showing why he does the job that he does)
Cruze beats up dorn
Lord of the smurfs kills one of the twins (maybe but as alpha legion win everything most likely not)
All of them think logar is a loser
Cruze eats humans, but doesn't really like the taste
Logar beats the Fulgrim daemon to pulp