Complete Monster: Gul'dan finds out Kil'jaeden is a genocidal demon lord but still follows him for the pursuit of power, not caring a jot for the fate of his people. When Ner'zhul discovers (to his horror) what he has done, Gul'dan rats him out to Kil'jaeden and puts the kibosh on his attempts to salvage the situation. Afterwards, he becomes the new "spiritual leader" and manipulator of the orcs. He never shows a shred of remorse, just fear that he might not get all the power he wants.
The draenei are reduced to this as a species. Their culture is almost destroyed, 80% of their population is wiped out and only literal divine intervention saves them from utter extinction. Not to mention that the orcs were initially turned against them by slanderous, blatant lies Kil'jaeden spread about them among the orcs to make the subsequent war of genocide seem like the right course of action.
Ner'zhul. An unwitting pawn of Kil'jaeden's plans, he never intended to set his people's downfall in motion and was deceived by the face of his deceased mate Rulkan, but the orcs have to drink the blood of Mannoroth and become The Horde, or the events that followed in the games and beyond wouldn't make any sense; worse yet, only does he get Mis-blamed by the real Rulkan and the other ancestors, but his earnest attempts to undo his mistakes are halted by Kil'jaeden. And to top it all off, he gets betrayed by his own apprentice, Gul'dan, then forced to watch as his people devolve into mindless ragemonsters, unable to do a damn thing about it. Poor guy.
Durotan. At first he goes along with his people's plans to ensure orcish unity and strength, but his attempts to be the Token Good Teammate end very badly for him and his clan.
