Pictures shared online show an Avengers fan struggling to sit up on a blood-stained pavement outside a cinema.
Fans had been waiting in a lengthy queue to see the three-hour epic in Hong Kong, AsiaOne News reported.
The victim began to shout spoilers outside the cinema, ignoring the pleas from directors and actors not to ruin surprises for patient fans.
Angered filmgoers allegedly attacked the man in a bid to stop him from revealing any more details of the record-breaking flick.
Fans have been quick to react on social media, with one commenter saying: “These fans aren’t playing, people have been watching 21 films for over a decade…Don’t be a d*** and start screaming out s*** after the movie ends”.
However, another fan said: “As much as I hate spoilers I think these fans may have overreacted a bit.”
“Remember, Thanos still demands your silence”
The Russo Brothers
Endgame directors the Russo brothers previously pleaded with fans not to spoil the ending in an open letter.
They said: “To the greatest fans in the world, this is it. This is the end.
“The end of an unprecedented narrative mosaic spanning eleven years and eleven franchises.
“When you see Endgame in the coming weeks, please don’t spoil it for others, the same way you wouldn’t want it spoiled for you.
“Remember, Thanos still demands your silence.
“As always, good luck and happy viewing.”
Dedicated social media users have previously got the #dontspoilendgame trending on Twitter in a bid to stop leaks.
Passionate Avengers fanatics have reacted so strongly to the finale of the saga that one woman in China was reportedly hospitalised for crying so much.
The film has already smashed box office records for ticket sales, besting Star Wars: The Force Awakens.
The highly anticipated superhero epic is expected to top the two billion dollars made by the Marvel’s previous effort, Infinity War.