Well to be fair, Kai Leng wasn't as bad as the catalyst kid. Deus Ex Machina is annoying in any game, but then you assign a random kid to that role and you activate my infinity hate mode.
Also Witcher 2 main enemy guy was really boring. The makers just decided to max all his attributes and call it a character. "oh, he is a muscular fighter. AND a wizard! AND a master of plots! AND does parkour! He is the perfect bad guy!"