The brother of Frieza, he watched Frieza destroy planet Vegeta. After Frieza was defeated he went to earth seeking revenge against Goku. Cooler like his brother can transform. Unlike his Brother, Cooler can transform one step further. Unfortunately for Cooler this wasn't enough to beat Goku and was thrown into the sun by Goku. However, half of Cooler's head still survives and floating in space.
In movie 6 he merges with an alien ship and revives with a robotic body. Tried to take over planet Namek, he fails of course and is killed by Goku this time for good. Actually, the chip that Cooler needed to come back was crushed by Vegeta making sure that Cooler never come back thus making Vegeta the one who killed Cooler.