Jackie Chun was actually Master Roshi in disguise. Goku, in his first ever tournament, lost to Jackie Chun by a single point.
Here's a breakdown:
* Goku and Jackie Chun fought in the final round of the 21st World Martial Arts Tournament.
* The fight was incredibly close. Goku landed several powerful punches, but Jackie Chun countered with his own impressive techniques.
* Jackie Chun ultimately won by a single point. He knocked Goku off the platform using his signature "Drunken Fist" technique.
* Goku learned a valuable lesson about respecting his opponents and the importance of strategy.
It wasn't until later in the series that Goku learned Jackie Chun was his master, Roshi, all along.