Throughout every era of the Goku has gained incredibly strong power-ups and increasingly impressive transformations, and while it may not be the strongest among them, one form stands above the rest as being the perfect one for Goku: Super Saiyan 4.
Super Saiyan 4 is the fourth level of the Super Saiyan transformation, but it is unlike the others in a number of ways. To accomplish SSJ1-3, a Saiyan of considerable strength needs to amass an enormous power level and then simply focus on the transformation itself through sheer determination and will. The method to achieve Super Saiyan 4 is a bit different from that. Firstly, a Saiyan who has already reached at least SSJ1 has to become a Golden Great Ape under the light of the full moon (or an equivalent) and then take control over their minds–which is immensely challenging given the inherently primal nature of the Great Ape transformation itself. Then, and only then, can a Saiyan reach Super Saiyan 4, a process that is more tedious than the Super Saiyan God ritual–but in the end, Goku proves that it’s worth it.
Goku’s Guard Can Be Down While as a Super Saiyan 4 (Eliminating His Shortfall)
In Dragon Ball GT episode 35 (written by Atsushi Maekawa, directed by Osamu Kasai, produced by Toei Animation), Goku is in the middle of his fight against GT’s most powerful Machine Mutant villain, Baby. Baby has possessed Vegeta and effectively became the fusion-form of Baby-Vegeta–a fighter with all the strength of Vegeta with the added power of Baby (who, for reference, is more powerful than Majin Buu just by himself). In this episode, Goku has already gone through the rigorous process of becoming a Super Saiyan 4, and Baby-Vegeta attempts to take him out quickly as he can sense Goku’s insanely high power level. Baby fires a devastating blast at Goku–in fact, he fires a number of them in sequence–but Goku doesn’t move. He doesn’t dodge or block, Goku simply stands there, as he has become so powerful, those attacks have no effect on him even if he has his guard completely down–which, as many fans know, is perfect for Goku.
Goku is notorious for letting his guard down during a fight. This is how Goku lost his fight with Majin Vegeta in Dragon Ball Z and how he nearly died during his battle against Frieza in Dragon Ball Super. In fact, this negative trait is something that he is currently working on with his angelic trainer, Whis, as it is officially Goku’s greatest flaw as a warrior. While Goku is on his way to mastering a form called Ultra Instinct which allows him to dodge and counter any attack without thinking, Super Saiyan 4 does him one better as he doesn’t have to dodge at all, he can just take practically any blast to the face and be perfectly fine.
Obviously, Super Saiyan 4 Goku isn’t invincible and has to put up a fight against god-tier beings, but every past situation where letting his guard down almost got him killed wouldn’t have been a problem if he were a Super Saiyan 4. The surprise attack from Vegeta wouldn’t have had any effect, and the sneaky sniper-blast from one of Frieza’s henchmen wouldn’t have phased him. This means that Goku is free to put his guard down as much as he wants once he’s made the SSJ4 transformation, and for this reason, Super Saiyan 4 is Goku’s perfect Dragon Ball form.
