TMZ Sports has obtained video of Pacman Jones in a full-on FIST FIGHT at the Atlanta airport -- showing the NFL star retaliate violently after he was attacked by a man who works at the airport. 

Cops told us the altercation began when the ABM employee -- Frank Ragin -- made a gesture toward the NFL star as he was walking through the airport with a female companion. 

You can see in the video ... Pacman (real name Adam Jones) calls out the guy and confronts him.  

Ragin -- still wearing his orange airport vest -- goes after Jones, initiating the fight. 

Jones tries to take off his backpack, but instead throws a haymaker at Ragin. The two exchange shots until Pacman lands the knockdown blow with an overhand right, sending Ragin to the floor. 

After Jones landed a few more shots, the fight was broken up. 

Cops responded and arrested Ragin -- claiming he was the instigator and Jones was simply defending himself.