Nerlens Noel -- I Didn't Trash That House ... Denies Death Threat

Nerlens Noel says he's NOT the renter from hell -- claiming allegations he absolutely destroyed the Philly home he was renting last year are pure B.S. ... adding that he never threatened to kill the owners.

TMZ Sports broke the story ... the 76ers star was sued for more than $40,000 by the property owners who say the 22-year-old trashed the place so bad, the place looked like a bomb went off inside.

Among the accusations ... carpet destruction, toilets clogged with cotton balls and feces, water damage, broken appliances and allegations he left a tombstone on the front step as a death threat.

Now, Noel has finally fired back in legal docs of his own -- adamantly denying he went "Project X" on the place. In fact, Nerlens says he tried to work with the owners to repair the carpet damage even though he wasn't entirely convinced he damaged them in the first place.

But Nerlens is clearly most upset about the tombstone allegation -- insisting it was just a Halloween decoration that was left on the property a few weeks before the holiday ... and doesn't amount to a threat.