Omega Five

Just beat the first stage of the game with any character in arcade mode. Avoid staying near the Yeti-Snow Machine during both encounters as it can do major damage and is hard to dodge. The boss is fairly simple. Learn the patterns of the three formations and you should get through just fine.

Tip from MyAbolustion:
"Another tip for Stage 1, you can essentially end the boss battle immediately if you save up an entire chip set (3 100%s). As soon as the boss appears jump into the centre of the square so it encloses you inside of it. After a few seconds, the boss should become hittable and you should unleash 3 consecutive ultimate bursts. The boss will instantly die because the burst will hit every single corner piece from the inside."