Struggle (わるあがき, Vain Struggle) is a damage-dealing Normal-type move introduced in the first generation. It is a move that cannot be learned naturally by any Pokémon. However, every Pokémon can use it, but only if all of their moves cannot be used, usually due to a lack of PP.
If the Pokémon has no more moves it can perform, it will perform this attack. It does typeless damage dealing quarter of the damage as recoil to the user (in Generation III and prior, it was half). Since it is typeless, it does neutral damage to every type, unaffected by STAB and will bypass Wonder Guard. The recoil damage cannot be ignored by Rock Head and other similar abilities or items. Struggle also ignores accuracy and evasion stat changes as of the fourth Generation.
No Pokemon can actually learn this move, but every Pokemon knows this move when the PP of their moveset run out.