Before engaging in battle with Blackheart, survey the area for six glass structures. Destroy each of these structures to give your team an advantage. If any of the six remain and you defeat Blackheart he will just regenerate. The structures will emit an energy blast if you get to close, so use ranged attacks to destroy them. Blackheart's two main attacks are a radial ground smash and a ranged energy beam, both of which knock your characters back and down. Once his regenerators are destroyed it's much easier to defeat Blackheart.