Mamoswine

Mamoswine has a huge Attack stat, and its excellent dual STAB gives it perfect coverage outside of Bronzong, some forms of Rotom-A, and Shedinja. It also can pick off faster Pokemon and deal severe damage to a multitude of common threats with its STAB Ice Shard. Mamoswine has a usable Defense stat, but its Ice typing and low Special Defense means it can't take too many hits. Mamoswine also has rather low Speed, so it's somewhat reliant upon either Tailwind, Trick Room, or Thunder Wave support. Overall, Mamoswine's excellent Attack stat and fantastic coverage make it a hugely powerful attacker if given the right support.