Raditz

"You were born on the Planet Vegeta. You are a space fighter, a Saiyan Warrior. Just like me.  Allow me to introduce myself, I'm Raditz.  Your big brother."

"I see the fire in your eyes, brother; you should come with us. It's in your blood, you love to fight."

- Raditz to Goku.

"You are a disgrace to all Saiyans! Now, prepare to die!"

- Raditz to Goku.

"After all, he's my nephew. It would be a shame if I had to hurt him."

- Raditz threatening to kill Gohan.

Raditz is the older brother of Goku and the first villain in the series Dragon Ball Z and in the Dragon Ball Z Kai series.

He is one of the last surviving members of a race known as the Saiyans, and comes to Earth in search of his brother, to see if he had taken over Earth, as he was supposed to. However, Goku hit his head as a child, and lost all memory of his mission and who he was. Raditz is also the first Saiyan to come to Earth, and at that point he was much stronger than Goku, and Piccolo, who had teamed up to fight him.

Past
Raditz, along with Nappa and Vegeta returned from their conquest on the Planet Shikk. However, when they returned, they were met with insult rather than congratulations by Dodoria, Zarbon, and Frieza. While Raditz was visibly hurt and angered by this, Nappa loses control and attempted to attack all three. But Vegeta orders his comrade to stand down, knowing that he would not stand a chance against them.

Arrival on Earth
Upon arriving on Earth, Raditz encountered a farmer, who tried to shoot him, but Raditz caught the bullet and sent it back at him, killing him. During his search for Goku, Raditz encountered Piccolo, whose attack had no effect on him. Raditz was about to use an attack called "Keep your eyes on the birdie" when his scouter picked up Goku's power level, and he headed off to find him.

Raditz and Goku
When Raditz finally found Goku, he was shocked to see that his brother has changed. He told Goku, and his friends that he's from another planet and that he's an alien called a Saiyan. He also told them that he, Goku and two others were the only members of the Saiyans.

Confrontation
Raditz kidnapped Goku's son Gohan to make him rejoin the Saiyans. Goku and Piccolo teamed up to fight him, but Raditz was still stronger, managing to destroying one of Piccolo's arm. Piccolo was left with no choice but to use his ultimate attack, The Special Beam Cannon, but Raditz dodged it. He then attempted to use his "Keep your eye on the birdie" again, but at that moment, Goku snuck behind him and grabbed his tail, causing him agonizing pain. However, he tricked Goku into letting him go, then stomped on him.

Raditz's Defeat
Gohan unleashed his hidden power and broke free of Raditz's space pod (where Raditz had locked him), and hit Raditz with his head, damaging him. As Raditz was about to kill Gohan, Goku gets him into a full nelson, sacrificing himself to defeat Raditz as Piccolo used the Makankosappo on them, mortally wounding them both. However, Raditz did not immediately die from this attack; after his scouter transmitted what Piccolo said about the Dragonballs to Nappa and Vegeta (and Frieza), he was laughing at Piccolo, who then finished him off.

This was also the beginning of the Z Fighters Vs. the Planet trade organization.

Powers and Abilities
Like nearly every villains in the Dragon Ball series, Raditz can fly, generate multiple Ki Blasts, and possesses superhuman abilities. He, like every other Saiyan, can only turn into a Great Ape during a full moon.

Great Ape
Raditz can transform into a Great Ape when he looks at the moon, absorbing Blutz Waves. This form multiplies his power by ten.

Soul
Spirit Raditz is a form of Raditz which appears in Attack of the Saiyans, it is the form Raditz takes in Otherworld, and in this form, Raditz is strong enough to take on Goku (who had finished training with King Kai), Gregory, and Bubbles.

Personality
Raditz is brutal, mean, intolerant, prideful and bitter. He loves to fight, just like all Saiyans, and he will gladly kill any member of his family if it means coming out on top. Despite being a heartless brute, Raditz is a coward in the face of death. To prevent being killed by Piccolo's "Special Beam Cannon", while Goku twists his tail in order to subdue him, Raditz "promises" to leave Earth and never come back. Because of his naivety, Goku releases him and he fights back.

Trivia

 * Piccolo_kills_Raditz.jpgz's actual death was never shown onscreen (as the last we see of him, Piccolo is raising his fist above him to deliver the deathblow), and his corpse remains offscreen when Bulma and Krillin take his scouter, suggesting that it was not a pretty sight what Piccolo did to him. His body is, however, seen from a distance at times (particularly the titlescreen of the episode), and clearly seen in the redub, and the ground around him appears cracked and damaged, though there are no visible markings on it as to how or where the deathblow was struck. Dragon Ball Z Budokai Tenkaichi suggests that Piccolo smashed him with his fist to kill him. It is in fact possible, though unlikely, that Raditz survived.
 * (Edit Firefoxray 10/8/14 10:15 PM EST, Raditz died as it said in the original anime and manga that Raditz went to hell but put up a fight, in which King Yemme stopped him.)