Kiokameha
The Kiokameha is an energy blast when the user uses a Kaio-ken then charges up a Kamehameha the Kaio-ken's energy has to go into the kamehameha's energy ball. It does massive damage but, you nolonger are in a Kaio-ken state. Goku almost used one against Vegeta but, he stayed with his Kaio-ken state. It is hard to control and there are only 3 known users. Trunks, Central Kai, and Goten. All of them used it during the Majin Wars.