This is going to sound weird, but...
You know what this reminded me of? The scene near the end of A Spell For Chameleon where Trent finally figures out Bink's secret Talent (He can't be hurt by magic), but simultaneously deduces that said power can't stop him from simply stabbing him with his perfectly ordinary sword.
But, exactly, couldn't Nemesis Kid adapt to Projectra's strength? Did she zap him with some psychic mojo he didn't know she had? Did the fact that she stood up to that punch with (for all intents and purposes) a "fuck you" freak him out that badly?