User blog comment:Monkey.D.Me/Care to Dare/@comment-3119203-20120425162459

Like they said, Whitebeard was old, sick, and mortally wounded. Sure he was pissed, but at that point, he didn't have enough power to take down Akainu in one hit. And even if he was young, Akainu is an admiral, one of the streongest figures in One Piece. He isn't stronger than Whitebeard, but he can take a few hits and keep on going.

However, Akainu being weaker than Whitebeard is when the old man was in his prime. Akainu is in the peak physical condition of his life, and Whitebeard is in one of the weakest conditions of his life. Therefore, at the time of Marineford, I think that they were relatively equal in power. In an extended fight, they probably both would have come out badly.