Complex sentence: In his final bout, he demonstrated his exceptionally hard punch by staggering powerful George Foreman, but was unable to capitalize on it; again showing himself deficient at basic self protection, Cooney suffered a devastating second round knockout that ended his career.
Split into simpler sentences: In his final bout, he demonstrated his exceptionally hard punch by staggering powerful George Foreman, but was unable to capitalize on it. Again unable to protect himself when in trouble, Cooney suffered a devastating second round knockout that ended his career.