Lord Foul
Brutal match up for any mind readers and basically anyone with supernatural senses <_< One of his servants touching you can overload your brain if you have the ability needed to properly feel it and you're not ready for it, and he kind of makes them (and by "them" I mean disembodied spirits who lived on after their bodies died through sheer spite, so they're pretty unnatural nasty bastards to begin with) look gentle. Looking into his mind is going to ****ing hurt, not to mention that trying to control his powers in any way will corrupt you into serving his will, and any attempts at mind control just mean you can't beat him anyway. Also kind of interesting to see how Mewtwo himself would handle to being on the receiving end of illusions, but really I think the most likely course of action here is Mewtwo gets royally messed up due to attempting telepathy, possibly taking him out of action but certainly screwing him up way too hard to focus on properly defending himself.
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We clasped our hands, our hands in praise of a conquerors right to tyranny