Hagler has a high ko percentage, but he seems to be a guy who scores knockouts from an accumulation of punches. How would you describe his power, and who among middleweights hits harder, and who doesn't?
He really committed to throwing combinations. If he threw two pretty hard punches, you always knew a third was right behind those. Until late in his career when inactivity and age dulled his skills, he never lunged with big shots that threw him off balance. Combinations, combinations, combinations.....
I'd rate Haglers power in the 7.5/8.0 range. He isn't a 1 punch KO artist but mostly all his punches were delivered with sharp consistent power. As for who hit harder ? Fighters like Jackson, McClellan, Benn, come to mind immediately.