Frieza

Frieza is one of the most powerful and evil beings in the universe. When he learns about the DragonBalls, he is crazed with the idea of wishing for immortality. Knowing and fearing a Saiyan's ability to become more powerful after injuries and battles, he decided to wipe out the entire Saiyan race by destroying planet Vegeta. Little did he know that four Saiyans were still alive(Goku, Vegeta, Raditz and Nappa). Frieza is extremely powerful and strikes fear into those when even his name is mentioned. Even though Frieza is defeated on Namek by Super Saiyan Goku, he later returns to Earth with his father King Cold to get revenge against Goku and the other Z warriors. Little does he know that Trunks was there and that he would be the one to finally kill Frieza. Frieza later returns when everyone escapes from HELL or should I say HFIL, and is once again destroyed by Gohan.