Complex sentence: Gendo shoots Ritsuko fatally and tries to merge with Rei who however, remembering Shinji rejects Gendo by severing his hand instead of his arm and absorbs Adam and merges with Lilith on her own.
Split into simpler sentences: Gendo shoots Ritsuko fatally and tries to merge with Rei. Rei however, remembering Shinji rejects Gendo by severing his hand instead of his arm and absorbs Adam and merges with Lilith on her own.