I would have to say Omega Shenron. Here's why:
First of all: his Ki starts off as, and automatically fills to, "MAX"
That is an unfair advantage right-off-the-bat. Here's a technique that I've used to get the maximum amout of Zenie.
Go to the "World Tournament: Advanced", and Select Omega Shenron. Now, set his skill tray to "Sparkling !!!!!!! (7)". When the match starts, slide all the way back to the edge of the ring. The second your opponent tries something, teleport behind him so they are knocked out-of-bounds. You can do this to win the entire tournament!!! It may take a few teleports for some opponents, but this strategy works!!!!! As the champion, you will receive 250,000 Zenie!!!
I'll be the first person to admit that this is a cheesy way to win,...but hey: this is the computer we're fighting. None of you can honestly tell me that the computer doesn't "cheese" you from time-to-time!!!!
CHEESE-BACK!!!!!!!!!!!
Death is but a door, Time is just a window,...I'll be Back!!!!!