Wladimir Klitschko stops Kubrat Pulev in Round 5.

World heavyweight champion Wladimir Klitschko is known for his devastating right hand as well as his ram-rod left jab. But his left hook? It doesn't get nearly as much attention but it is equally as destructive. Klitschko used that powerful left hook to record all four of his knockdowns in a one-sided, fifth-round annihilation of mandatory challenger Kubrat Pulev on Saturday at the O2 World arena in Hamburg, Germany - the same city where Klitschko made his pro debut 18 years ago.It was another sensational performance for Klitschko, who retained his title for the 17th time in his second reign as he continued to move closer to a pair of hallowed boxing records. more