Frieza is one of the most evil and powerful fighters in the universe. We first see him on the planet Namek, where he is forcing the local residents to give him their Dragon Balls so he can wish for immortality. You might notice that I'm using the pronoun 'he.' Even though the voice in the American version bares a striking resemblance to that of a female's, believe me, Frieza is male. Frieza is the leader of an organization known as the Planet Trade, who sells planets to customers after destroying all of the planet's inhabitants. Frieza was always paranoid that the legendary Super Saiyan would emerge among the Saiyans, so he destroys the planet Vegeta, leaving only four remaining Saiyans in existence. The four were Vegeta, Raditzu, Nappa, and Son Gokou (Kakarotto). Of course, Son Gokou becomes a Super Saiyan and defeats Frieza... or so we thought. One year later, Frieza, along with his father King Kold, comes to Earth in the form of a robot and threatens to destroy the world. He is then decisively defeated by a mysterious youth, a Super Saiyan, by the name of Trunks.

Vegeta

The father of Trunks and the husband of Bulma, Vegeta shows a tough front but is full of pride. At first he is a villain, but like most villains in Dragon Ball, he is quick to join the "good" side. But even after Vegeta joins up with the Z fighters, he is still very reserved and won't accept pity. He doesn't talk to anyone much, and utterly despises Son Gokou. Vegeta can't stand him because of the simple factthat Gokou is stronger than him. So, Vegeta is constantly trying to be better, but never truely succeeds. He is the third (if you count Trunks) person to become a Super Saiyan, and one of only two to achieve Super Saiyan 4. You might be asking, "If Vegeta's heart isn't pure, how did he become a Super Saiyan?" The answer to that is simple: Vegeta does have a pure heart... it's just pure evil. He finally becomes truely good in the Majin Buu saga where we get to see a side of him that was once thought to be non-existent. He swallows his pride in a tough situation and acknowledges that Gokou is stronger than him. Vegeta might seem hard and cold on the outside... but, well, I guess he's that way on the inside too. But every series needs a badass, doesn't it?

Piccolo

The evil half of Kami-Sama, Piccolo really isn't all that bad. At first he is extremely evil, wanting to take over or destroy the world. He attempted to kill Son Gokou on a number of occasions, each time being defeated, and each time vowing to get his revenge. Butsomething, or maybe someone, changed that. Because of Gohan (who had been training with Piccolo for a year), Piccolo learned to love, and almost completely abolished his evil. Piccolo becomes one of the "Z Fighters" during the fight with Vegeta, and protects Gohan with his life. He fuses with Nail during the Android saga in order to defeat Freeza, and stays fused for the rest of the series. Also, when Androids #16, #17, and #18 come to kill Son Gokou, Piccolo fuses back with Kami-sama in order to defeat them. Piccolo maintains a substantial role throughout all three series, and is an important asset to the show.

Gohan

Gokou and Chichi's first son, Gohan shows phenomenal power at a very young age. The key to his strength is anger; whenever he gets extremely angry, Gohan unleashes all the power within him, surpassing even his father at times. When he was only five years old, he was trained by Piccolo for an entire year, who had seen the great promise in Gohan's strength during the fight with Raditzu. During that year, Piccolo and Gohan form a unique bond, making Piccolo a sort of second father to him. Later in the Vegita Saga, Piccolo even sacrifices his life to save his Gohan's. As he grows older , he learns to become a Super Saiyan at about the age of 12, and because he becomes enraged during the fight with Cell, he is the first to surpass the Super Saiyan level (SSJ2). Seven years afterward, Gohan enrolls at Orange Star High School where he meets his wife, Videl. Gohan and Videl have a daughter named Pan at the end of DBZ.