Bob has a real abusive move, which is really simple and will get you through the whole game really easy. Pick him solo, so he has more health. Then on the final battle, die on purpose now swap to Bob and another character of your choice. Preferably someone your half-decent with, but it shouldn't matter.
Hold Back and push both LP and RP (X+Y Default).
You'll do a combo starting with a headbutt and then two more hits, it's really powerful and will make short work of the Arcade mode.
Set your Options to Easy and 1 Round too. The final boss you'll have to do over 2 rounds but just use the combo.
Advanced:
To make the abuse even easier, you can use BACK then X then Y. This will punch them in the stomach twice and leave them keeled over ready for a Headbutt combo. Your all ready holding BACK, so just hit X+Y together.