Pac has been hit with some heavy artillery but probably not as accurate and powerful as KT's straight right. This is one punch southpaws have to watch against right handers. The converse is true with Pac's left. KT has a decent chin and PAC wouldn't be able to blow him out early. KT could possibly KTFO PAC chicken dance style but once again that is possibly unlikely. In the end Pac's workrate might get him a decision, but I wouldnt be surprised if either one KOed the other. Most likely Pacman in a great fight.
This would be a great fight as both have similar styles and power. I think Kostya's reflexes might give him a better defense. So I'd put my money on him. But Manny could get to him first. Either way a great fight and quite a chin tester.
Tzsyu, this isn't competetive. Cotto (natural lefty), Hatton (tiny t-rex right, reliant on jab and left hook), Oscar (natural leftie again) - all have awful right hands. Marquez - good right hand. Tszyu destroys him.
Pac wins via Decision. I think both have decent beards, both will have there moments in a few brawls. But Pac might just beat him on workrate.