Freeza was the first true villian to fight the Z Warriors.(yea I know they fought vegeta and nappa first but vegeta joins the z warriors and vegeta kills nappa) Freeza was the one who destroyed the planet Vegeta(saiyons home planet) He was considered the most powerful being in the universe. Even King Kai thought this.
The Z Warriors were having a hard time defeating Freeza. Then finnaly Goku came and helped them out. Despite Gokus efforts Freeza stilled held his ground. That all turned when Goku turned Super Saiyon. Freeza was finnaly destroyed when the planet Namek was blown up. However Freeza was recreated by his father King Cold. But was destroyed by the sword of Trunks.
Freeza was very powerful yet weaker then all the other villians. He could transform into three other stages each increasing his power by millions.