In Disgaea 4: A Promise Unforgotten for the PS3, there are eight characters you can unlock by beating the extra battles in the game.
You unlock these extra battles by passing bills for them in the senate.
Asagi – Beat extra battle Six
Axel – Beat extra battle One
Etna – Beat extra battle Four
Flonne – Beat extra battle Two
Kurtis – Beat extra battle Seven (after meeting him multiple times in Item World)
Laharl – Beat extra battle Five
Raspberyl – Beat extra battle Three
Zetta – Beat extra battle Nine
