Aside from his final show of power in his final Dragon Ball appearance in the Dragon Ball Super: Super Hero movie, Piccolo has been sidelined against the other heroes and villains he was once on par with, this which is a far cry from his early days in Dragon Ball where even the gods of their world secretly viewed Piccolo as a greater threat than even Frieza.
When he was introduced, Piccolo wasn’t a Dragon Ball hero – in fact, he was one of the cruelest villains in the franchise’s history. Piccolo began his career as a being who saw himself as a literal demon, King Piccolo, whose one and only goal was to throw the world into chaos and inspire horrific acts of violence in every citizen. Before he can take over the world for any significant amount of time, Goku kills King Piccolo, but before the villain dies he produces an egg containing his reincarnated form – the version Piccolo fans know and love today. While the reincarnated Piccolo has completely redeemed himself for the evil deeds of his previous life, he obviously hasn’t earned everyone’s trust by the time Frieza arrives.
In Akira Toriyama’s Dragon Ball Chapter 314, Goku and Frieza are in the middle of their iconic fight on planet Namek. Meanwhile, Piccolo stands in the distance with Krillin and Gohan, watching the fight and ready to step in if it looks like Goku needs him. In this chapter, Goku loses pretty badly to Frieza, and the Saiyan decides the only move he has left to play is the Spirit Bomb. When Goku begins this technique, Piccolo is stunned as he has no idea what Goku is doing. It’s not until Krillin tells Piccolo that King Kai taught Goku this move during their last training session that Piccolo finds out about the Spirit Bomb’s existence. Piccolo even curses King Kai right now for showing Goku and not him despite Piccolo only training with King Kai, saying, “He never told me about that…”.
King Kai is a god over an entire sector of planets in the Dragon Ball universe, and he has been watching Earth for a very long time. Because of this, King Kai knows exactly how destructive Piccolo can be if he wanted to, which is probably why King Kai decided not to share this specific technique with him as it has the potential to destroy an entire planet without barely exhausting the user. any power since Spirit Bombs draw ki from those around it rather than just that one person. However, Piccolo was just training with King Kai for the sole purpose of becoming powerful enough to kill Frieza, so it seems King Kai really should have shown Piccolo everything he knew to ensure that Frieza would be defeated. – but the fact that he did’ indicates that King Kai is secretly more afraid of Piccolo’s potential than Frieza’s current threat level.
It makes sense that King Kai wouldn’t want to help make Piccolo more powerful than necessary, given the specifics of Piccolo’s past. Not only was Piccolo a villain who believed himself to be a literal demon, but he was also the embodiment of every ounce of evil expelled from the body of the Earth God, Kami. So Piccolo was not just a Namekian gone bad, but the concentrated negative by-product of a mortal reaching the level of a god, and King Kai – being a god himself – knew exactly how much. point something like that is really dangerous. Frieza is a murderous tyrant and scum of the universe, sure, but King Kai still saw Piccolo as a much bigger threat in Dragon Ball – and the fact that he didn’t teach him about the Spirit Bomb while he really should have proved it.