Tell him he is not playing his character. His character gains abilities that he has trained in. If he doesn't use the abilities, why did the character get them in the first place? You could go a little heavy-handed and have the Raven Queen appear to him in his sleep and outright tell him that she didn't give him his Lay of Hands features to never use them - there are actually people whose time to die is yet to come, and she has plans for them. (Something like: "You see this Fighter friend of yours... He nearly died in the battle against the Kobolds. But he survived, and now is stronger then ever, and even more capable of bringing death. I want him to stay alive until he has served his purpose...")
And if he's actually saying he wants to "prove that the system is broken" tell him this is not an experimental play-test simulation scenario, this is a role-playing game and people want to play an enjoyable game, not have it intentionally disrupted by him.
Since he seems to generally like disrupting the game, I would highly recommend talking a serious word with him and tell him how you feel about it. If he doesn't care whether he hurts your or your fellow players enjoyment of the game, you should seriously consider throwing him out. That might be a hard choice, but I am convinced you will be better off.