Poliwrath

Poliwrath's ugly typing and unremarkable stats give it a lot of trouble in RBY OU, but access to the rare Amnesia gives it a real niche as a wallbreaker. Unlike Amnesia users such as Slowbro and Snorlax, Poliwrath lacks the stats and typing to become unbreakable, but its Speed gives it a niche over them. Poliwrath outspeeds Exeggutor and can nail it with Blizzard after some chip damage, rather than having to fear Sleep Powder and Explosion like the other Amnesia users in the tier. It also possesses immediate threats against Chansey in the form of Hypnosis and Submission, which OHKOes with a critical hit.

However, while Poliwrath possesses these advantages over Slowbro, it suffers from all of Slowbro's flaws and more. It needs a lot of setup to break past Starmie and Chansey, which often threaten it with Thunderbolt, and it is vulnerable to Psychic, making Pokemon like Alakazam and Jynx much more problematic than they are for Slowbro. Like Slowbro, even after setting up, Poliwrath needs to watch for enemy Explosions that can stop the party before it even starts. Perhaps most importantly of all, Slowbro is able to heal itself throughout the game and provide utility thanks to superior defensive stats paired with Thunder Wave, while Poliwrath does not possess the bulk nor the movepool to be anything other than a one-time breaker.

Nevertheless, Poliwrath's Hydro Pumps deal incredible damage after only a few turns of Amnesia, which it can often find against paralyzed or sleeping foes, and it is capable of taking down multiple Pokemon in a single game if its primary checks, usually Starmie and Chansey, are either KOed by teammates or statused and weakened enough to be handled by Poliwrath itself. While inconsistent, Poliwrath is a Pokemon that can lead to good results if you build towards its strengths.