Malefor in The Legend of Spyro trilogy really qualifies for this position. He destroys the dragon eggs to find a purple dragon, gets one to make it one of his henchmen, and tries to destroy the world. If that wasn't enough, he even tries to kill the titular character with his own love interest. By the way, in order to make him monstrous, he is played by The Joker. He does intend to destroy it so it's replaced by an entirely pure universe, but even so, it's inexcusable.
Even worse is when Fridge Horror takes effect with said dragon he took to make a henchman. Think of it this way: she's the only dragon in the series to have metal blades and wing claws instead of bone; think about it. Then realize she was, at the oldest, 11 or twelve when it must've happened.
The Sorceress in Year of the Dragon is an interesting case. Her first act, stealing every unborn dragon, is pretty Kick the Dog, but in a later cutscene, we're led to believe that she's a Well-Intentioned Extremist by Bianca. However, in the very next scene, the Sorceress chastises her for thinking this, stating that she wants to kill three hundred infant dragons for their wings, which she will use for a spell to make her live forever. When the horrified Bianca asks why she has to kill them, she replies that she doesn't; she just doesn't want them squirming around when she cuts off their wings. This one line prompts Bianca to pull an immediate Heel Face Turn.
