Rivalry

Rivalry is an ability present in the Pokémon series that directly influences the damage output of the Pokémon possessing it based on the gender of its opponent. Here are the key details and effects of the ability:

Effect: When a Pokémon with Rivalry faces an opponent of the same gender, its attack power increases by 25%. Conversely, if the opponent is of the opposite gender, the Pokémon's attack power decreases by 25%. If the opponent is genderless, there is no change in the power of the Pokémon's attacks.
Mechanics: The increase or decrease in power applies to both physical and special attacks. This ability effectively makes gender-matched battles more favorable for Pokémon with Rivalry and can significantly impact battle strategies, especially in competitive play.
Interaction with Moves: Moves that do not rely on gender, such as status moves or those used against genderless Pokémon, are unaffected by Rivalry. This makes it important for trainers to consider the

Effects

This Pokémon inflicts 1.25× as much regular damage against Pokémon of the same gender and 0.75× as much regular damage against Pokémon of the opposite gender. If either Pokémon is genderless, damage is unaffected.

Flavor Texts

diamond-pearl: Raises Attack if the foe is of the same gender.
platinum: Raises Attack if the foe is of the same gender.
heartgold-soulsilver: Raises Attack if the foe is of the same gender.
black-white: Deals more damage to a Pokémon of same gender.
black-2-white-2: Deals more damage to a Pokémon of same gender.
x-y: Deals more damage to Pokémon of the same gender.
omega-ruby-alpha-sapphire: Deals more damage to Pokémon of the same gender.
sun-moon: Becomes competitive and deals more damage to Pokémon of the same gender, but deals less to Pokémon of the opposite gender.
ultra-sun-ultra-moon: Becomes competitive and deals more damage to Pokémon of the same gender, but deals less to Pokémon of the opposite gender.
lets-go-pikachu-lets-go-eevee: Becomes competitive and deals more damage to Pokémon of the same gender, but deals less to Pokémon of the opposite gender.
sword-shield: Becomes competitive and deals more damage to Pokémon of the same gender, but deals less to Pokémon of the opposite gender.
scarlet-violet: The Pokémon's competitive spirit makes it deal more damage to Pokémon of the same gender, but less damage to Pokémon of the opposite gender.