Sean O'Malley beat the hell outta Jose Quinonez this weekend ... dropping him with a devastating head-kick that Suga compares to being SMASHED in the dome with a solid wood bat.
TMZ Sports talked to O'Malley -- fresh off a 1st round TKO at UFC 248 -- and the 25-year-old star walked us through the combination that left Quinonez in the fetal position on the Octagon floor.
"That head-kick ... that was a powerful and heavy head-kick! It's pretty much like if I had a baseball bat. I swung as hard as I could at him.