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Deals damage and lowers the user's Special Attack by two stages.
Overheat is an incredibly powerful Fire-type move. However, so much sheer power comes with a high price, as after usage it will sharply reduce the user's Special Attack, making them easy opportunities for enterprising opponents. For this reason, it fits a more hit-and-run playstyle often preferred by Choice users. Unfortunately, Fire-types have that nasty weakness to Stealth Rock and considering that Choice users have to switch out a lot by nature, it can prove troublesome. Anyhow, Choice Specs Heatran gets an honorable mention because it is bulky, hits hard, and is neutral to Stealth Rock, so is a very good candidate if you are using a technique of this sort.
Fire Blast is a slightly less powerful and less accurate alternative with no negative effects.
Flamethrower is a much less powerful but more accurate alternative with no negative effects.