Vegita & Trunks
Vegita
Vegita is the "bad guy among the good guys." He first made his appearance back when Gohan was 4. Although he fights alongside the other Z fighters, he is still decidedly evil. As the prince of the Saiyajins, he is very proud, has a huge ego, and is constantly trying to prove that he is the best fighter in the universe. Vegita has a continual rivalry with Goku, or "Kakarott," (Goku's Saiyajin name) and is obsessed with beating him in combat just to show that he is the stronger. This obsession with trying to be stronger than Goku proves to be a fairly large weakness as well. Despites his efforts to show otherwise, Vegita has changed and has developed a conscience, and deep down cares about his friends. Furthermore, he is also somewhat emotional at heart. He demonstrates this when dealing with his son Trunks, most notably just before he died trying to kill Majin-Buu. Although he pretends to hate Goku with a passion in reality he respects his power and maybe even likes him a bit. Trunks
Trunks is Vegita's son. In his future, all of the Z fighters were killed by the Artificial Humans, except for Goku, who died of heart disease. Trunks travels 20 years back in time to give medicine to Goku so he can survive this disease and defeat the Artificial Humans. Trunks' returning in time alters the past in other ways which can be seen later. After giving the medicine to Goku, Trunks goes back to his own time, but returns again three years later to help the Z fighters battle the Artificial humans. During this time, he becomes extremely powerful and surpasses every other one of the Z fighters except for Gohan and (maybe) Goku.
The Trunks here, "Future Trunks" and the "current Trunks" are radically different characters. "Future Trunks" is very polite like Gohan and has very strong values, but the current "Chibi Trunks" has a bad attitude and is somewhat like his father. Chibi Trunks never truly reaches the power level of his future counterpart; possibly because he lived through mostly peaceful times, whereas Future Trunks did not