13 minutes. Basically, you have to go berserk. don't give him a chance to attack, and when he does, reverse it. when he reverses your attacks, counter the reversal and come back strong. use fatalities as often as possible, about 6 spinecrushers killed him last time i tried it (without using other attacks). it get's easier when you know how to avoid getting hit with any attack. one thing i've noticed is that countering a trip reversal still damages you slightly, therefor, only use trips when the enemy is stunned, or has just gotten back up. another trick is jumping over a trip instead of reversing it. to do this tap space when you would normally tap shift. you should land before he has recovered from the wasted attack, and will be able to soccer kick him, or U punch him. This does more damage than reversing the trip. another good idea for overpowered enemies is to use the wall kick a lot. it cannot be countered/reversed, only dodged, it does high damage, and stuns them badly. you can also try bunny kicking the enemy right as he gets up, this gives them a lot less time to reverse the kick. try to use bunny kicks when the enemy is close to a wall, hitting the wall will increase the damage done, and stuns them more. When there are dead bodies around use the corpse cannon to hit live enemies with the dead ones, this does about the same damage as a bunny kick, and cannot be reversed, unfortunately, it's harder to hit the target, but is quite effective when there is a successful hit.
anyway, done rambling.