The fighter I would use is Nightmare. The brave edge combo called Death Lord's Annhilation is one of the easiest in the game.
Just press the following:
<- K, A+B+K then B
[ Xbox 360 controls: <- B, RB then Y]
You can go through arcade and get it there.
It's possible to get 3-5 brave edges per match depending if you win or lose. That said, it shouldn't take too long to get 100.