The connecting record
shownOne Punch Man · ch. 77, pp. 17-20
Watchdog Man beat Garou in One Punch Man.
Garou runs, and is chased as far as the edge of Q-City.
What each of them is ranked on
The winner · Watchdog Man · rank 7
Guardian of Q-City
Went through thirty Monster Association monsters at once in the street and came out of it unmarked, with Garou arriving to find him sitting on the pile. When the two of them fought later, Garou could not account for the speed. Holds one city and does nothing else. He sat at C-class rank 301 and is S-class now — moved up when the S-class was formed, a reclassification on the day the top of the ladder came into existence rather than a climb through it.
shownOne Punch Man · ch. 67, pp. 25-28
Tears apart thirty Monster Association monsters that surround him and finishes without a scratch.
shownOne Punch Man · ch. 77, pp. 17-20
Blocks everything Garou throws, wounds him severely while holding back, and drives him out of the city.
statedOne Punch Man · ch. 77, pp. 17-20
Garou says the speed far exceeded what he had expected.
All 6 citations
statedOne Punch Man · ch. 122 (Online), pp. 17-18
Was C-class rank 301 until he was moved up when the S-class was formed.
shownOne Punch Man · ch. 122 (Online), p. 17
A flashback to his early career draws him ripping the head off an enormous monster and taking no injury.
statedOne Punch Man · ch. 20, p. 7
Q-City is described as the most dangerous city by the number and average disaster level of its monsters.
Beaten · Garou · rank 2
Hero Hunter
Put down the S-class hero Tanktop Master, and had Metal Bat bleeding and broken and about to be finished when the hero's sister walked in and stopped it — both while still an unenhanced human, having been thrown out of his master's dojo months earlier for hospitalising the rest of the students. After contact with "God" he copied Saitama's striking power outright, and the pair of them had to be moved off the planet before their fists met, with the released energy pushed away from Earth by four people afterwards.
shownOne Punch Man · ch. 47, pp. 11-14
Beats the S-class hero Tanktop Master after a barrage of punches.
shownOne Punch Man · ch. 58, pp. 32-40
Dodges and deflects everything the S-class hero Metal Bat throws, moving faster than Metal Bat can follow.
statedOne Punch Man · ch. 30, p. 5
Bang says he beat Garou and expelled him from the dojo after Garou disabled the other students.
All 10 citations
statedOne Punch Man · ch. 81, p. 17
Tells the heroes ambushing him that he has beaten close to a hundred of them.
shownOne Punch Man · ch. 77, pp. 17-20
Watchdog Man beats him and drives him out of Q-City.
shownOne Punch Man · ch. 169, pp. 53-55
Takes on Cosmic Fear Mode after contact with "God".
shownOne Punch Man · ch. 173
Withstands repeated Serious Punches and keeps fighting until Saitama's output outgrows him.
shownOne Punch Man · ch. 172, pp. 3-10
His Serious Punch collides with Saitama's, and Blast and three others divert the released energy away from Earth.
statedOne Punch Man · ch. 171
Blast warns him that in this state anything he does could end life on Earth, and he is unbothered.
statedOne Punch Man · webcomic ch. 55, p. 1
The webcomic also rates him a Dragon-level threat.
What this does not settle
One fight in one work. It is the only result the record gives between these two, and it is evidence about that meeting and nothing wider — not a general matchup, not a rematch, and not a ranking of its own.
The ladder above it is argued from everything either of them has been shown doing; this page is argued from one citation.
Where the two disagree, the disagreement is the point, and it stays visible rather than being resolved by whichever of them happens to be on this page.