Unburden

 is an Ability that boosts a Pokémon's attack speed if it isn't holding an item.

Effect
If the Pokémon isn't holding an item, their attack speed is doubled.

Pokémon with

 * Hitmonlee
 * Treecko
 * Grovyle
 * Sceptile
 * Drifloon
 * Drifblim
 * Purrloin
 * Liepard
 * Accelgor
 * Swirlix
 * Slurpuff
 * Hawlucha