An ex-MLB player was SO PISSED about nearly being beaned during a Venezuelan winter league game Wednesday ... he straight-up turned around and attacked the catcher with his bat!!!

The wild scene all went down during a heated matchup between Aguilas del Zulia and Caribes de Anzoategui -- where pitchers were throwing at batters all night.

But, in the 8th inning ... Aguilas outfielder Alex Romero -- a former Arizona Diamondback -- had enough of the bean wars -- and weaponized his bat after he was nearly struck in the back with a fastball.

The video is NUTS ... 36-year-old Romero takes TWO hacks at Caribes catcher Gabriel Lino -- and then all hell breaks lose.

Lino threw his glove at Romero ... the benches cleared -- and fighting could be seen all over the diamond!!!

Eventually, the umps were able to calm things down ... and ejected several players after the brawl -- including Caribes infielder and Minnesota Twins stud Willians Astudillo.

Reportedly, players will face heavy fines and suspensions over the altercation.