Freeza is the second main villain in DBZ.
He appears on planet Namek searching for DragonBalls
as well as Vegeta and Son-Gohan with Bulma and Krilin.
First Freeza appears along with many servants, whe number of which,
go to zero soon after Vegeta got to know that Freeza was the
one to destroy his planet. Though before they all ware killed by Vegeta
they've done many violent things. The main Freeza'a servants ware Dodoria
Vegeta tried to fight Freeza, but he appeared to be much
stronger, and Vegeta lost. Only after Goku came to Namek, Z Team
( With Vegeta on their side ) started to take over.
Goku and Freeza ware fighting that hard that Namek, as the planet
crashed, but Goku succeded to escape, after reaching SS2 level.
Freeza was thought to be dead.
Though this was untrue, Freeza appeared again, on Earth
with King Cold on his side, but they all ware easely defeated by Trunks
who came from Future. After that Freeza appeared only couple times in DBGT
part in hell, and haven't coused a lot trouble.