Generation V
Contrary
Makes stat changes have an opposite effect.
Detailed Effect
Whenever this Pokémon's stats would be raised, they are instead lowered by the same amount, and vice versa.
Pokémon With Contrary
13 canonical Pokémon forms can have this Ability.

Inkay
Malamar
Mega Malamar
Mega Staraptor 
Shuckle
Spinda
Snivy
Servine
Serperior
Fomantis
Lurantis
Enamorus Incarnate
Lurantis Totem