What do you think of his Spanish accent?

I would say it too if I wanted to sound cartoonish, but I would say it with a funny accent, not "seriously" as he said it.

Anyway, I highly doubt he grew up in a "South American country".

This guy intentionally spoke Spanish slowly because the listeners were Koreans who are studying Spanish(lower-intermediate level).

The guy mostly grew up in Argentina; he spoke Korean at home with his parents but except that he always spoke Spanish.
He came back to Korea 9 years ago and since then he has been living in Korea so his Spanish might became rusty.

He speaks Korean fluently but he has an awkward accent when he speaks Korean and he sometimes chooses wrong words or expressions.

do you have another voice file we he speaks proper Spanish?