Torment
Move 1
Torment
Move 2
Substitute
Move 3
Protect
Move 4
Lava Plume
Taunt
Item
Leftovers
Ability
Flash Fire
Nature
Calm
EVs
244 HP36 SpA12 SpD216 Spe
Torment, combined with Heatran's impressive set of resistances and considerable bulk, turns Heatran into one of the toughest Pokemon to KO in the game. The idea behind this set is that not many Pokemon carry more than one attack powerful enough to break Heatran's Substitutes. With that in mind, Torment allows Heatran to stay safe by using Protect to prevent its opponent from breaking its Substitute with their STAB or super effective attack. That means that every other turn, Heatran can attack with Lava Plume for free without having to worry about being damaged. This set slowly chips away at Heatran's opponent while maintaining Heatran's Substitute at the end of the duel when they faint.
Lava Plume is the move of choice on this set, due to its high PP and 30% burn rate. Many Heatran switch-ins (such as Gyarados, Tyranitar, and Swampert) do not like getting burned. The chance to burn also helps slowly drain the opponent's HP, meaning Heatran does not even have to attack. Instead, it can alternate between Substitute and Protect to rack up residual damage. Taunt is an interesting option over Lava Plume for dealing indirect damage. It prevents Pokemon from healing and forces them to attack Heatran's Substitutes in vain. When combined with Torment, Pokemon such as mono-attacking Blissey and Suicune will struggle every other turn, allowing Heatran to beat certain Pokemon that would otherwise completely counter it; however, Taunt also makes Heatran lose to other Pokemon which Heatran would normally be able to beat. In fact, any Pokemon with more than one attack, or a faster Pokemon with Taunt will be able to beat this set unless they are afflicted with a status condition.