And Bradley also said Matthysse hit him harder than anyone he's ever been in the ring with and that was with huge sparring gloves. So is Matthysse an 11.
It is no surprise that Lucas and Ruslan hit harder than Pac. Like Clottey said about Pac, it is not so much the power but more about the speed of Pac. Pac is a solid, fast puncher. Ruslan and Lucas are much slower but have devastating power.
The KO power comes from being able to hit opponent quick enough for him to be able to expect it or being able to hit from an angle your opponent does not expect. Everyone can hit a heavy bag hard, but being able to make a good connection with power on an opponent that tries to avoid you is what makes some boxers special. It doesn't matter how hard you can hit, if you are predictable and your punches can be defended/avoided. Timmah fought much more cautios fight(s) against pacman than he did against provodnikov and there is an obvious reason for that...