Klitschko was known for his powerful punches and durable chin. With an 87.23% knockout percentage rate, he holds the second best knockout-to-fight ratio of any champion in heavyweight boxing history, after Rocky Marciano's 87.76% and is the 8th longest reigning heavyweight champion of all time. He has never been knocked down in any professional boxing bout. His two losses have come via a shoulder injury during a fight and a deep cut below his eye, which were recorded as RTD and TKO losses. In both fights, however, he was leading on the scorecards. Klitschko was the first professional boxing world champion to hold a PhD degree. His power and his possession of a doctorate have led to his nickname, Dr. Ironfist. More: en.wikipedia.org.