When it comes to kind-hearted and friendly anime and manga characters, there are few who match the big heart of Goku. He's willing to fight for the sake others and to protect not only his loved ones, but the entire planet Earth and even the whole universe. However, he wasn't always the Saiyan with a heart of gold like he is today. In the original Dragon Ball, Goku was a terrifying kid. He still fought for good, but he ended up crossing the line more times than a hero should -- even if he never meant to.
As a child, Goku seemed harmless and innocent on the outside, with his short stature, non-threatening appearance and even his tail. However, it cannot be overlooked that he is a descendant of the Saiyans, a proud race of warriors. He may not have had memories of his family or Planet Vegeta, since he was a baby when he landed on Earth, but he wasn't able to shake his Saiyan instinct. That became especially apparent whenever a full moon was out and he transformed into a Great Ape. In this beastly form, Goku went on a rampage, destroying everything in his path with zero control over his actions. This stopped once Goku's tail got cut off but, by then, he'd already accidentally killed his adoptive grandfather, Gohan. Goku wouldn't even realize that he'd killed his grandpa until his fight with Vegeta many years later.
But even in his normal child form, Goku was a force to be reckoned with. In his fight against King Piccolo, Goku managed to punch a hole right through him with only one good arm, killing the evil Namekian. Goku also managed to take out the entire Red Ribbon Army all by himself. All of the soldiers he defeated were either armed with guns or flying weaponized aircrafts, but Goku took them all down with surprising ease -- even for him.
Given how much power he had and the mayhem he caused as a kid, it's amazing that Goku stayed on the path of good for as long as he did. He may not be the smartest Saiyan around, but he is certainly the purest of heart, which is why, despite having these incredible abilities, he's been able to use them to fend off villains for many years. In his adult years, he's even reluctant to kill most bad guys unless it's absolutely necessary.
Even though he's grown up to be an admirable hero, it can't be denied that Goku was a scary child. It's unthinkable that someone as young, small and naïve as he was had the ability to wreak so much havoc. Thankfully, those days are long gone and more importantly, Goku's sons didn't turn out the way he did as a kid.
