Aerodactyl

Aerodactyl is the engine of the Round chain: its maxed Speed stat (32 SP) and Jolly nature make it one of the fastest Pokemon in the format, ensuring it fires Round before opponents can act. When a second Pokemon uses Round on the same turn, Round gains first-turn priority and jumps to base 120, turning what follows into a pseudo-priority move for Mega Pidgeot and Sylveon. Focus Sash guarantees it survives to fire Round at least once. Outside of Round, Rock Slide spreads chip with flinch potential, Ice Fang patches Flying-type coverage, and Dual Wingbeat handles Fighting and Bug types. Unnerve prevents opposing berry consumption.