>>50803940This.
It's the Piccolo/Vegeta effect.
You show how strong this new guy is by having him (or, commonly, one of his underlings) effortlessly beat up an established powerful character, if not the main villain/rival of the previous, or a recent arc, to show how much higher the stakes are now.
In the short term this builds up a dramatic moment, especially when Goku shows up and oneshots the guy who effortlessly beat up the guy Goku barely beat last time.
In the long term it weakens the character, and creates unfortunate patterns where Piccolo's entire job is to get the shit beaten out of him for the first round until the end of time, and beating Piccolo just means they've passed the "you must be this tall to ride" sign.
Pokemon has just had trouble with the concept of object permanence to remember a character long enough to do this.
