Alvin Kamara reared back and punched a man repeatedly during a violent altercation inside of a Las Vegas hotel earlier this year ... new video, obtained by TMZ Sports, shows.

But, sources connected with Kamara say the video doesn't tell the full story, claiming the alleged victim became violent first.

The incident happened back on Feb. 5 ... inside The Cromwell Hotel and Casino.

According to an October lawsuit filed by Darnell Greene, the altercation all went down after he and the New Orleans Saints superstar got into an argument outside of an elevator of the hotel's popular Drai's Nightclub.

Greene alleged he tried to get on the lift with Kamara and Kamara's associates. But, he claimed in his suit the football player barred him from getting on by "throwing his arm across Greene's chest," and then brutally attacking him.

In the new footage, you can see Kamara -- wearing a light shirt and signature dreads -- throwing multiple blows at Greene.

The clip shows the punches ultimately took the man to the ground. While down, the video shows several other men jumping into the attack -- kicking and stomping the guy, before clearing out.

The footage appears to match pictures that Greene's attorneys included in the lawsuit against Kamara last month. According to the suit, as a result of the beatdown, Greene suffered injuries to his neck, back, head, shoulder, knees and face ... including "a disfiguring facial fracture to" his right orbital bone.

Greene is suing Kamara for $10 million.

Kamara, meanwhile, was arrested following the 2022 Pro Bowl game for his alleged role in the incident ... and charged with felony battery resulting in substantial bodily harm and misdemeanor conspiracy to commit battery.

At the time of the arrest, cops claimed in police documents that Kamara did admit to punching the man.

Kamara -- who's had an up-and-down season for the Saints this year -- is due back in court for a hearing on the case next week.