Complex sentence: After discovering that Atlantis had agreed to complete subjugation under Superman, Aquaman confronts and defeats Flash, Shazam, and his alternate counterpart before Ares sends him to rejoin the others and assist the insurgents, which includes a Lex Luthor who didn't indulge in illegal activities.
Split into simpler sentences: After discovering that Atlantis had agreed to complete subjugation under Superman, Aquaman confronts and defeats alternate versions of Flash, Shazam, and his alternate counterpart. After Aquaman gets his answers from him, the alternate Ares sends him to rejoin the others and assist the Insurgents which includes a Lex Luthor who didn't indulge in illegal activities.