If you don't like psionics, you shouldn't allow them in your campaign. Now, it seems, you're stuck. It is unethical to deliberately attempt to kill off a particular character, but if you wanted to, all you have to do is analyze his typical strategies. What would the party do if an evil psionic warrior showed up using these tactics against them? They would find a way to survive, surely. Just use PC-nasty tactics against him.
No character is invulnerable. Figure out how to deprive him of his strengths and emphasize his weaknesses.