Willie McGinest Sued -- Allegedly KOs Man ... Hurls Gay Slurs

7:00 PM PT -- A rep for McGinest tells TMZ Sports the NFL star adamantly denies the allegations.

"Simply put, each and every allegation in this lawsuit is false. Willie's record as an upstanding member of society and his service to youth sports and giving back to the community speaks for itself."

Willie McGinest is being sued by a man who claims the ex-NFL star not only knocked him the hell out like Deebo in "Friday" ... but has terrorized him verbally ever since.

TMZ Sports has obtained a lawsuit filed by DeAndre Parks -- who claims Willie went ballistic on him back in October 2015 ... punching him in the face so hard he was knocked unconscious.

When he came to, the man claims Willie "continued to taunt [him] by laughing and boasting that he punched [him] with his left hand, insinuating that his left hand was his weak hand."

Fast forward to Sept. 2016 ... when the men ran into each other at a youth football game in which Parks' son was playing -- and Willie allegedly ordered him to leave and had other attendees run him out.

Parks claims the cops were called -- and he left without further incident.

But things came to a head again on Sept. 23rd -- when Parks claims he was confronted by Willie at another youth football game ... and Willie went berserk.

Parks claims Willie threatened to fight him again -- and called him all sorts of names including "punk," "buster," "bitch ass n**ga" and "f**got ass n**ga."

Parks says Willie also said, "You getting knocked out all over town."

Parks says he's afraid to go to police because he doesn't want to be seen as a "snitch."

Now, he's suing for more than $25k for medical expenses and other damages.