After Roxas goes thru the door, he asks:

Roxas- Hello. Who are you? Reveal yourself.
Kaxaw lands in front of him.

Kaxaw- So, this is our showdown, huh?

Roxas- Yeah, it is. And, don´t espect me to go easy on you. DathKepper, Oblivion.
Oblivion reborns in Roxas hands.

Roxas- Let´s figth, buthole.
They rush at each other. Parrying, blocking, attacking. After only 2 minutes everything is covered in Darkfire and debris. 
Roxas-Give up yet?

Kaxaw-NEVER!!!!
They continue to fight. 
Roxas-Time to finish this!

Kaxaw-Just what i was going to say!

Roxas:
LIMIT BREAK!!!
There is a flash of light. Suddenly, Roxas is in what appears to be a Anti-Form and Kaxaw is glowing with darkness. 
Kaxaw- Let's finish this.
Roxas growls and pounces. They continue fighting. Roxasstops, tires. Kaxaw stops in the middle of the dark power. 
Kaxaw- Bring it on!
Roxas nods, then chuckles. He turns around. There is a flash of light, then Roxas is seen pouding on Kaxaw with his claws. Then Roxas stops, again. Then transforms back. 
Kaxaw- HA! I can take anything you can dish....
Kaxaw suddenly has a scared look on his face. 
Kaxaw- No. I absorved too much darkness.
Kaxaw transforms into Dusk.

Roxas- Time to go look for the Door to Ligth.
A portal opens, and Roxas goes thru it.