how to unlock Hercule (Mr. Satan) Character
If you want to unlock him you need to get to level 50 with Gohan, Trunks, Vegeta and Piccolo. Look for the gates which are marked "50" to collect the character trophies for each character.
Piccolo's is New Namek, Trunks's is West City, Vegeta's is the Northern Mountains, and Gohan's is just outside Gingertown.
If you want to have a new ending
Get to level 50 with Hercule (Mr. Satan) and break down the Level 50 door to KKTV in West City.
enjoy ;)