Nerlens Noel Sued -- WORST RENTER EVER ... Weed, Gatorade Stains & Death Threat (PHOTOS)

NBA star Nerlens Noel puts the guys from "Project X" to shame -- DESTROYING the home he was renting last year with Gatorade stains, drugs and toilet damage ... this according to a lawsuit obtained by TMZ Sports.

The 21-year-old Philadelphia 76ers star rented a 4,800 square foot home outside of Philly back in September 2014 -- paying $54,000 for a one-year lease. But he not only trashed the place and left weed throughout the home ... he also allegedly threatened the owners after he moved out.

In their lawsuit, the owners of the home list all of the crazy damage they found including after Noel moved out in August 2015:

-- "Splashed neon colored sports drinks (such as Gatorade) on the carpets throughout the home."
-- $30,000 in other damage to carpets
-- Extreme water damage throughout the home
-- Clogged toilets filled with cotton balls and feces

(In fact, the owners say the plumber who fixed the toilet told them the damage was so bad he told them, "Someone must not like you.")

-- Broken elevator (it's a baller house)
-- $4,000 in damage to the stove
-- damage to the fridge
-- damage to the blinds
-- damage to dishwasher
-- torn window screens

The owners say they also found weed and roaches from joints in the home -- including pieces of marijuana in the master bathroom drawers.

Now here's the scary part ...

The owners say they demanded $42,000 to repair the damage ... but the DAY AFTER they sent the demand, a TOMBSTONE with the words "RIP" mysteriously appeared on the front steps of the property. The owners believe it was Noel's doing and are considering it a death threat.

They're now suing Noel for all sorts of reasons -- including assault (because they believe harm is imminent) and want more than $75,000 for their troubles.

As for Noel, so far no comment from his camp -- but according to the suit, he's demanded his security deposit back.