I Torched All of Nick Young's Clothes

Hell hath no fury like Iggy Izalea scorned -- just ask Nick Young, who had all his clothes LIT ON FIRE by his ex-GF ... after he got caught with his pants down.

"I burnt it all. And I threw stuff in the pool, too," Iggy said, smiling.

Remember -- the NBA baller and rap star had a pretty messy breakup back in the day ... and we already knew Iggy dumped a bunch of Nick's crap on her driveway (and got his car evicted).

And now, we got the play by play of Iggy going pyro on all of Swaggy P's designer clothes.

"I texted him a video and I’m like, 'Hey, I’m burning your s**t ... I don’t know where you’re at, probably with some girl, so I hope you get home quickly because I’m moving on."

"We're…