Saiyan Level Info

The Saiyans are from the former planet Vegeta. People there were extremely powerful, but very barberic. It was claimed to be destroyed by the guardian of that planet, but really, it was Freeza. The only Saiyan that servived were Vegeta, Raditz, Nappa, and Goku(Kakarot). They then worked for Freeza to conquer planet for them. Good thing for Goku, our hero, he had suffered memory lost as a child and forgot about his destructive objective.

Super Saiyan
Goku was the first to achieve this stage. To transform to a Super Saiyan, a Saiyan must build up anger within themself. When the transfomation works they should have gold hair which spikes up and their eyes turns green. A golden glow also surrounds the Saiyan. In addition to the changes in the looks, their power, speed and agility greatly increases.

Ultra Super Saiya-jin

Description: This stage is between SSJ and SSJ 2. During this stage the Saiya-jin's muscles greatly increase in size. The Saiya-jin becomes very strong, but also very slow.  Attacks would do a lot of damage, but it is unlikely to hit the opponent. When Goku and his son, Gohan were training in the Room of Gravity and Time during the Cell saga, Goku demonstrated this stage to Gohan, and told him that it was useless because of it's drawback of making a saiya-jin usually slow. This stage's disadvantage is demonstrated as Trunks fights Cell and is beaten.

Those who achieved this form: Goku, Mirai Trunks, Brolli, Vegeta

Super Saiyan 2
This stage is easier to achieve than the transformation to Super Saiyan. One must work and trainer harder to become Super Saiyan 2. The changes in their looks is that their hear is shorter and is more seperated. And again, their overall abilities increases.

Those who achieved this form: Goku, Gohan, Vegeta, Trunks, Goten and Brolli

Super Saiyan 3
Great power and strenght are required to transform into this stage (similar to those needed to transform to Super Saiyan). The result of this is the increase length of their hair, and their muscle is bigger. Oh, and their eyebrows are gone, making them look "intense" and vicious.

Those who achieved this form: Goku and Gotenks

Super Saiyan 4
This is the most powerful stage of all. Their hair turns black (again), the tail grows back, and most of their body seems to be covered with a red coat of fur. And add to that, their power level extremly increases.

Those who achieved this form: Goku and Vegeta

Ozaru

Description: When a Saiya-jin with a tail is exposed to pure moonlight (from any moon) he turns into a gigantic 20-foot tall, ape-like creature. The Saiya-jin's power level is increased ten times when turning Oozaru (Oozaru is the Japanese word for "Big Monkey") Saiya-jin's used this form to take over planets for Freeza. This form is possibly the most powerful form under SSJ level 3.   All saiya-jins, except Goku and Gohan were able to control themselves during this form.

Those who achieved this form: Goku, Gohan, Vegeta, and other saiyans that took over planets for Freeza

Golden Ozaru

This stage is much like the regular Oozaru stage except that the fur is golden not brown and it's of course much stronger. This is also made by TOEI. To reach this stage a Saiya-jin must have a tail and must receive more waves from the moonlight. The only ones to ever reach this stage was Goku and Bebi Vegeta during Dragonball GT. Vegeta reached it while Bebi was inside of him and attacked his friends. He was eventually defeated by Goku.

Those who achieved this form: Goku and Bedi-Vegeta