Super Saiyan 4 (Imperial Wyrm)

Super Saiyan 4 is the next form after Super Saiyan 3. Goku briefly transformed into a Super Saiyan 4 during the six months after Kid Buu, but before Beerus. The form was draining his life force, though, so he never used it again. Super Saiyan 4 is nearly as strong as a Super Saiyan God, however, Goku didn't use it against Beerus because of the effects it had on the body. When a user reverts from the form, some of their life force has been drained and their body is damaged. Super Saiyan 4 is thus the limit of Super Saiyan without the use of god ki.

Appearance
The users hair is as long as it is in Super Saiyan 3 form, but it sticks up completely, and has no bangs. The hair is also white instead of golden, but the form still has a golden aura. No eyebrows are visible, much like Super Saiyan 3, and the eyes are the same color. The users muscle mass increases a lot, so this form is very buff.

How to achieve it
It is achieved through intense training as a Super Saiyan 3, training so intense that it is life threatening. It is very difficult to achieve. One must first master Super Saiyan 3, then put force into powering up, so it is achieved much in the same way as Ascended Super Saiyan (a power up of the normal Super Saiyan form).