Very busy today with holiday business, but fortunately this doesn't take but the most cursory internet search...
“Wladimir Klitschko, all of us must know by now, may be one of the greatest one-punch fighters in history,” said Steward. “He is of the few fighters- and I have trained many punchers- who can turn off the light switch in the middle of a big party without doing the dimmer switch first. We saw in the Chambers and Ray Austin fights. He doesn’t have to get a guy in trouble but can knock him out with one single punch." Manny.
"To me, I knew he could still be the champ because he has that power. He has that power.” Ray Austin
“Klitschko had more power, most definitely. In both hands. You could feel it. Put it this way – if it would have been Wladimir in there when his brother fought Lennox Lewis, I think he would have dropped Lennox Lewis. I honestly do. I think he would have dropped Lennox Lewis.” Phil Jackson
“The strategy for this fight is real simple … create foot pressure, take his space away, like Wladimir did against Eddie Chambers. Cut him off, cut him off, cut him off. Create tension. Don’t give him time to relax. Shoot the jab, shoot the jab, shoot the jab and eventually you’ll get caught with a big shot.”
Thus, it’s no great surprise that Steward compares his punching power to that of giant-sized former protégé Lennox Lewis and most people believe he hits harder than Mike Tyson ever did. - ESB Interview with Steward
If you don't believe these guys, there are two pretty well vetted posters on here who have sparred extensively with Wlad. Both claim him to be the most effective power puncher they have faced, including the likes of Bowe, Tua, Lewis and Foreman the elder.
It's fine if you don't want to accept these opinions. Just don't think people are going to rate your opinion over these guys.