Lich king, because he can kill the whole raid with 1 button after testing them for a while, and I wont let nobody stop me from ressing them to the scourge
Mannoroth mythic. Line up your Fel Hellstorms with the Doom Lords Mark and it will most certainly kill several players. If that is not enough for them, then also use Felseeker on the Imp spawns. This means they either have to deal with spread out imps or they have to stack them in the felseeker. If they try to put felseeker towards the edges, just stop casting and push them off with shadowforce