Breaking Pokémon

Breaking Pokémon is one of the many features that can be a bit difficult to figure out. The option to Break a Pokémon will appear once the mon is at its final evolution and will look like an icon with wings (pictured below) next to the Pokémon's Power. Breaking a Pokémon will typically give a stat boost or improve an existing skill. To Break a Pokémon, you need another one. For example, to Break a Charizard to Gen.I Charizard, you need another Charizard. However, if you've already evolved your Charizard to its MEGA evolution and have not yet Broken it, you don't need another MEGA (thankfully). To Break it a second time you'll need two more Charizards, and four more for the third Break. Also note that you'll need to manually add your extra Pokémon when you go to Break one.

Breaking a Pokémon keeps all the stats (IVs, Base Stats, Friendship, etc.) that you put into the original Pokémon, and consumes one you are Breaking it with.