Slade will fight for awhile, then flee and let his henchmen attack you. You must defeat all henchmen before he will come out of his barrier. Slade has demonic powers received from Trigon. It is best to keep your distance from him. When he uses his charged attack, it will cause serious damage to anyone up close, hitting them three or four times. He will attack you three or four times before you can finish him off with your team charged attack.