Junior welterweight Luis Quinones tragically died on Thursday ... just five days after suffering a head injury during a knockout loss in Colombia. He was only 25.
Quinones was an undefeated boxer (10-0) until his matchup with Jose Munoz on September 24 at Coliseo Elias Chegwin ... when was knocked out with less than a minute left in the fight.
Video of the fight shows Quinones fall down after getting punched ... and he's unable to get back on his feet. He was then taken out of the ring on a stretcher by medical personnel.