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I was playing doubles and earth power only targeted one pokemon, i checked with Bulbapedia, and it said it was supposed to target all adjacent pokemon, so is Bulbapedia wrong, or Showdown?
Earth Power is only single target, while Earthquake hits all adjacent pokemon. It's likely that either Bulbapedia is messed up, or you searched up the incorrect move.
Earthquake targets all adjacent pokemon. Earth Power can target any adjacent pokemon, but only one. Earth Power on Bulbapedia says "May affect anyone adjacent to the user," whereas earthquake says "Affects all Pokémon adjacent to the user."