Heatran

Heatran is a niche bulky offensive threat thanks to its solid stats and great typing, bolstered by Flash Fire. This makes Heatran have an incredible matchup against most of the metagame, such as Flutter Mane and Gholdengo.

Rillaboom is a great partner for Heatran, as it resists Heatran's prominent weaknesses, while also hitting Pokemon like Ogerpon-W and Urshifu-R for huge damage. Heatran also pairs well with Ogerpon-W, which supports Heatran with Follow Me, as well as threatening Urshifu-R and Landorus.

Although Heatran resists a lot of attacks with its typing, it's weak to both of the Urshifu formes, Ogerpon-W, Landorus, and Iron Hands. Heatran also faces tough Fire- and Steel- competition, especially with Incineroar.