Nice 'n' easy fight, as it should be.
You can easily pound K-Fed into a pulp without taking more than a couple of punches. The key is to play the drums on his ribs and stomach, and ignore the face shots til it's time to finish him off. Britney's easily dispatched. Deliver a quick hook to the little demon-seed in her arms, then a few quick jabs to her face while he flies away. She'll be too stun-locked to catch him, and he'll fall to the pavement, at which point she'll scream somewhat like how a wounded elephant would sound, and drop back out of the slaughter. Finish tapdancing on Kevin's ribs til he's out of stamina, then take your time and decorate his face a bit. When you're done giving him a facelift, charge a punch and let him have it. You can juggle the head in the air if you like... I got 103 juggles before I finally missed one and let the head fall to the ground. From there, just move the mouse in the direction you'd like to pee in, and give it to him in the eye.
Overall? Very well built and entertaining game. 10 for you.