Greninja

Greninja's stats may seem mediocre, but much like any accomplished ninja, it's second to none at assassination thanks to a wide variety of unique tools! The most prominent of these tools is its ability Protean, which functionally gives it STAB on every attack in the game, more than making up for its mediocre offenses. Greninja isn't limited to just type changing shenanigans, as it is also the best user of the ability Torrent in Battle Spot Singles, being able to annihilate most offensive Pokemon with a Torrent-boosted Hydro Vortex from Hydro Cannon. Combine this with Greninja's incredible Speed stat, which allows it to outspeed Naganadel and Mega Salamence, and this puts the silent assassin among the deadliest offensive threats in the metagame!

Greninja may be a deadly offensive threat, but it has very lackluster defensive stats that make it very difficult to switch in. Even with Protean or Torrent making up for Greninja's low offensive stats, it still misses out on important KOs against Pokemon it hits for neutral damage and doesn't do particularly well against stall teams, meaning Greninja is a Pokemon that should not be used recklessly.