Task List/megaevo lv3
Did you keep track of which Mega Evolutions you're still missing? You can see in the PokéDex if an entry isn't complete. If the PokéBall shows 50% or, rarely, 33%, then you have the PokéDex entry of one possible forme, but not the other. You should see if the other entry is a Mega Evolution that you're still missing!
For more information on Mega Evolution, check the Wiki.