Complex sentence: She viewed Ultraman as a suitable replacement for the version of Superman who was her son back during the Absolute Power story arc and placed him under mind control so that he would believe himself to be Superman and her to be his mother.
Split into simpler sentences: She viewed Ultraman as a suitable replacement for the version of Superman who was her son back during the Absolute Power story arc. She then placed him under mind control so that he would believe himself to be Superman and her to be his mother.