Heatran

Heatran is able to find a niche in the Doubles OU metagame due to its unique Fire / Steel typing and a combination of its power and bulk. This allows it to check a variety of threats such as Mega Charizard Y, Mega Salamence, and Genesect. However, Heatran faces difficulty against generally specially defensive threats such as Tapu Fini and Zapdos that can shrug off damage dealt by Heat Wave and find opportunities to set up. In addition, Heatran's weakness to the common Water- and Ground-type attacks can allow opposing Pokemon to bypass its defensive capabilities and deal irreparable damage to it. Furthermore, a Speed stat of base 77 leaves Heatran outsped by a large portion of the metagame. Although Heatran doesn't have any glaring reasons to struggle in Doubles, these little flaws add up to making it tough to fit on teams.