Heatran

Heatran's nine resistances and two immunities give it a solid defensive niche and, combined with its bulk, let it take on popular Fairy- and Fire-type threats, such as Togekiss, Sylveon, and Mollux. Its movepool is nothing to scoff at either, letting Heatran pull off multiple sets, each with a different niche. With a Choice Scarf, Heatran is able to revenge kill many threats, such as Mega Metagross and Mollux. With a more offensive EV spread, Heatran is able to take advantage of moves such as Magma Storm and Solar Beam. However, Heatran's 4x weakness to Ground and weaknesses to Water and Fighting leave it vulnerable to many prominent threats, such as Colossoil, Landorus-T, and Keldeo, as well as being lured. Heatran's lack of recovery moves prevents it from walling threats forever and means it is easy to wear down over the course of a match.