One problem of course, I only did it once.
I decided to win the match again, just to win it legitly though

Oh, I found a good strategy while I was fighting my way to the top with Tarix, I found out the arena has boundaries(duh), and that there is a way to put them into a strategy. Move slowly to the back wall, making sure your opponent follows. When you get there, fight for a bit if you want, but try to turn so where you WERE is now where your opponent is trapped. If you're lucky, your opponent will just stand there instead of moving up or down, and you can just move in and out to attack him with light attacks before he attacks you back. You can get in like 3 or 4 or 5 attacks in a row in like this. I beat Gold Gresh with this method ^_^