Mimikyu

Although it's a quiet, lonely Pokémon, if you try to look at what's under its rag, it will become agitated and resist violently.

Ability — Shadow Box: Pokémon-GX that have any damage counters on them (both yours and your opponent’s) have no Abilities.

Tail Trickery (20): Flip a coin. If heads, your opponent’s Active Pokémon is now Confused.