>>45740766Hatterene's movepool is fine but leaves it with a massive, gaping weakness to Heatran (resists all STABS at x2 and x4, hits it super effectively back, and is not only immune to Hatt's most common coverage move for steels but outright absorbs it to boosts it's own fire attacks). It can do a lot, but Heatran completely destroys it unless you managed to rack up shitloads of CM boosts, somehow didn't get forced out before then, and the Tran manages to not crit you with Flash Cannon while you're trying to 3HKO it.
Hatterene can theoretically, however, beat Heatran if it's running Magic Powder, which is a gimmicky signature move that turns the target into a psychic type. This makes Tran lose the STAB bonus on Flash Cannon and it's resistance to fairy, which would allow Hatterene to beat it with fairy moves.
The problem arises from the fact that Magic Powder is a Powder move, i.e., it completely fails if it targets a grass type, meaning that running it over Mystical Fire means that Hatterene is now completely unable to beat Ferrothorn for the same reasons MF-Hatt loses to Tran.