Complex sentence: After the battle with Bardiel, wherein his father forced him to critically injure Asuka, Shinji retires from his duties and leaves NERV, but when Zeruel consumes Rei, Shinji returns and defeats the Angel by seemingly fusing with the Evangelion.
Split into simpler sentences: After the battle with Bardiel, wherein his father forced him to critically injure Asuka, Shinji retires from his duties and leaves NERV. When Zeruel consumes Rei, Shinji returns and defeats the Angel by seemingly fusing with the Evangelion.