Jackson was a small middle, in his prime at Jr. Middle. McClellan was obviously a huge puncher, but relatively unproven. I don't see what Hearns did, outside of the Shuler KO, that ranks him among the greatest hitters at the weight. A guy like Cyclone Hart hit at least as hard as any of them, in my opinion.
You would be on fairly safe ground if you picked Fitzsimmons, but others might deserve a mention such as Ketchell.
Bob Fitzimmons - a middleweight in a heavyweight's torso Stanley Ketchel -knocked Light heavyweight Phil jack O'Brien , out cold with one punch in 10th rd..Kod 49 out of 64 bouts. Julian Jackson- a great one ko puncher, but flawed...