This is extremely ironic. The same battle Spite evolved, was the one where one of my pokemon fainted for the first time. Before, I had always made sure to switch out when the health turned yellow, but I used a Burn Heal and took up a turn, so my poor Hurik (Excadrill) fainted. I used Spite for the rest of the battle, and, lo and behold, evolution. Proof that this game is a play-through fueled by spite and rage.