Contrary

Contrary is an ability in Polished Crystal that reverses all stat changes that are applied to the Pokémon with this ability. For example, if an opponent uses Growl to lower the user's Attack by one stage, the user's Attack will instead be raised by one stage. It also is supressed by Mold Breaker.

Careful though, if the user uses Shell Smash to raise its Attack and lower Defence, its Attack will instead be lowered and its Defence will instead be raised! Considering this ability is only found on Shuckle as its hidden ability, just be sure to check its ability before using any stat moves in high-stakes battles.