Change your preferences here.
Deals damage, but does less damage as the user's HP decreases. Base Power is calculated thus:
Base Power = 150 * (User's Current HP / User's Maximum HP), rounded down, but not less than 1.
Eruption has little competitive use. Not only are five out of the seven Pokemon who receive this move weak to Stealth Rock, all of them take full damage from Spikes and Toxic Spikes, so Eruption's Base Power will be lowered substantially when they switch in to begin with. Furthermore, Camerupt and Heatran have low base Speed, and if they takes damage before they can use Eruption, they are better off using Fire Blast or Overheat. Groudon does not receive STAB on Eruption, and moreover only has base 100 Special Attack to use it with, which is too low by Uber standards.
Fire Blast is a more reliable move with imperfect accuracy, but its base power is lower than Eruption's base power when the user's HP is full.
Flamethrower is a more reliable move, but its base power is lower than Eruption's base power when the user's HP is full.