Mr. Satan

Mr. Satan (or Hercule, depending on the versions) is a main character in Dragon Ball Z.

World Martial Arts champion, Satan is widely known all over the world as the strongest man alive, and a hero. He first appears during the Cell saga, to fight Cell who started attacking the planet. However, Satan is too much weak (especially compared to the Z fighters) and gets thrown out of the ring without even touching his "opponent", who merely paid attention to him.

During the following fights, Satan pretends to be ill, and that all the others are cheating. He however accepts to take Android 16's head to Gohan, which proves usefull since it convinced the boy to fight Cell with all his power. After the fights are over, Satan takes credit for killing Cell, and is labeled a hero.

Years later, Satan is called again to fight Majin Buu, and again is too weak to defeat him. Instead, he manages to become Buu's friend, and convinces him to stop killing. Though Buu later mutates in an even more dangerous monster, neither him nor Satan forget about their previous friendship. Thanks to this link and to his newfound courage (mostly when he starts believing the whole story is a simple dream) Satan becomes a suprisingly important ally to the Z fighters, helping them to defeat the Evil Buu once and for all.

Satan again takes credit for the victory, but still remains friends with the fighters and the good Buu, who comes to live with him.

Satan is the strongest "normal" human of the series, and has an incredible luck, since he not only survives all the dangers he goes through, but also gains fame for most of the heroes'acts. Though he is extremely arrogant, cunning, good liar and often clueless about what is going on, he still is very good-hearted and heroic when he has to.