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).