A Kansas City Chiefs fan was pummeled so hard during a wild brawl in the stands at Arrowhead Stadium on Sunday -- he appeared to be knocked out cold.
The violence all went down at some point during the Chiefs' game against the Chargers ... when K.C. fans got into a heated altercation.
In footage of the incident, filmed by bystanders, you can see the melee was all kicked off after one fan threw a huge haymaker amid a verbal argument.
That's when all hell broke loose -- 'cause several other fans ran into the area, throwing wild punches.
In the clip, you can see things got so bad ... a man appeared to be punched unconscious, with his limp body sprawled out over a row of seats.
Unclear if anybody suffered any serious injuries in the fight, or if any arrests were made. We've reached out to cops, but so far, no word back yet.
Of course, the brawl is just the latest in a long line of scraps at NFL stadiums this season ... remember, there were at least two huge altercations at SoFi Stadium earlier this month and one giant fracas at a Cleveland Browns game as well.
