I can only think that this was included to level things up a little when your granny picks up the control pad. You can also play the single player vs CPU mode without the strange assist mode activated where up to three rounds, lasting between 30 and 90 seconds, against up to 20 game characters may be played at a venue of your choice. Rather than offer three levels of difficulty you may disadvantage yourself or your opponent by adjusting the handicap bar. Survival and Challenge modes are battles against your own gang members for supremacy over their home turf. Defeat all other members and you may take on the Secret Gang Bosses, who if defeated, will be added to your roster of available characters.
Rumble mode seems to be the most fun to play.
First you must select a home team and then set about defeating all of the members of a rival gang. After every bout you may switch characters as long as they are part of your team. Should a member suffer defeat then they will bite the dust and be eliminated from the contest. There are also a couple of two player modes which are the standard one vs one contest or a two player Rumble. At first glance Vs. is a bit of a turn off, especially when faced with the rather chunky appearance of the characters.