That would be quite the battle.
From what I observed, Hancock cannot move as fast as Superman, so right away he has an advantage against him. I imagine the fight would be a lot like when Superman fought Captain Marvel, in the Justice League animated series. If Superman truly feels he has no other choice but to defeat his opponent for the greater good then, and only then, is the use of his full strength is justified. In an all out fight, Hancock would definitely need some kryptonite.
I was thinking about the power of Hanckcock though, it looks to be self giving and the only weakness is being around another like him. Superman has to get to the sun to get back his full strength but it didn't seem so with Hancock. Good point about the speed. Someone here mentioned speed being so underated since with speed you can accomplish so much long bfore anyone makes a move and I have to agree that is correct.
In Smallville, Clark's speed is hardly used to its potential. With speedsters like the Flash and Superman who don't need to rely upon acceleration to reach maximum speed, their reaction time would be phenomenal. Even if someone, tried to waylay them from behind as soon as the object made contact with the hairs on their head they would be able to move quicker than that object. Instinctively they would just move with it then out of the way and engage their opponent. A super fast person is pretty much untouchable, unless they are trapped and unable to maneuver or they fight someone as fast as they are.
"In the world of martial arts, speed is everything." (or something like that)
The Beast - 'Kung Fu Hustle'
I am surprised that this is not really addressed in any of the current super hero story lines, especially when even the old animated series, Dragon Ball Z always considered the incredible speed of the characters. Some of their battles were so fast could only be witnessed by other characters who could move as quick.