I saw this film around 2008. It was a Chinese film most probably. Frankly, it can be Korean or Thai film too. I could not identify them separately back then.
The plot goes like the following:
The hero's age is around 20s. He is possibly a kick boxer. A villain also runs some underground illegal kick boxing matches. The hero enters the championship because he needed money. Although a newbie, he fights well and defeats some of the villain's best guys. The villain becomes angry. The hero loves a girl. To save that girl from that villain, he fought with his guys.
At the end, it was found out that the girl was a double agent apparently working for that villain too. But her facial expression seemed sad. After defeating, some more great players, the villain starts fighting against him. At first, the villain beats him hard. When everybody is thinking, the hero is going to lose, he returns back into the fight. One important aspect of that final fight was the villain used metal nails in his finger grips to attack the hero and he cuts the hero using the nails as knuckles. This movement should be invalid in that match, but as the villain is the owner, nobody talks a thing. Anyway, at the end, the hero finishes the villain perhaps attacking with him nails too. It is also discovered that the girl started loving him and could not support the villain to kill him. But the villain forced her to support him.
I don't remember if any sword was used there. It was color and the movie was kick boxing based as far as I remember, but I am not sure.