Onyx was crushed by Crisis. All that he managed to do was give her a bad bruise that quickly healed. Ash being a stereotypical good guy, can't condone the (in his eyes) murder of his opponents. Even if it would be Team Rocket. Even if he wants Team Rocket to die for their constant, annoying evil acts that anyone with an ounce of common sense would see would have never worked anyway. And their stupid introduction that they won't stop saying no matter what. On second thought, maybe I could just look over there for a while, wink, wink.