1. King Piccolo.
King Piccolo is a frightening demon that has the power to spawn powerful demons by laying eggs through his mouth. He feels certain that with eternal youth, which he gets, he will be able to take over the world. He almost succeeds. Able to defeat Roshi and Tenshinhan, his only obstacle is a super-powered young Goku. He is proud, extremely confident in his strength, and terrifyingly cruel. He is the only Dragon Ball villain to rule the world albeit briefly.
2. Tao Pai Pai.
Tao Pai Pai debuts by killing General Blue by puncturing the side of his head with his tongue. He is a mercenary who kills for huge amounts of money. He also debuts the Dodonpa ray, a cousin of the Kamehameha. He is known for killing his opponents with extreme ease. He falls only to Goku after Goku has trained with Karin. (Unfortunately, he is decimated by Tenshinhan quickly when he comes back as a cyborg.)
3. Piccolo Junior.
He is many times stronger than the previous foe (his father King Piccolo). Have we heard this story before? He is also incredibly evil, but we do not see him actually take charge of Earth like King Piccolo did. Nevertheless, one cannot take away the fact that Piccolo Junior is the strongest foe in Dragon Ball. He also has a variety of interesting powers: the ability to stretch, grow into a giant, and repel the Mafu-Ba (a sealing technique).
4. Commander Blue.
Commander Blue is cruel and a sexually ambiguous stickler, executing a soldier for picking his nose. He also is has telekinetic powers. He is very strong and a badass, and he would have killed Goku and his friends had it not been for a distracting mouse scurrying around nearby.
5. Tambourine.
Tambourine was one of King Piccolo’s minions. He is the first villain to kill a main character, that character being Krillin. Tambourine is confident and his job is to hunt down and murder Strongest Under the Heavens Tournament competitors one by one. He is eventually stopped by Goku.