Pressure increases the opponent's PP usage by one when in battle. Additionally, when a Pokémon with Pressure enters the battle, a message broadcasting "<name> is exerting its Pressure!" will pop up before the battle menu appears. There are 14 Legendary/Mythical Pokémon with this ability and 5 Non-Legendary/Mythical Pokémon are with this ability.
Pokémon with this Ability