The connecting record
shownOne Punch Man
Saitama killed Carnage Kabuto in One Punch Man.
Chest, neck and head gone in a single blow, thrown because it was Saturday and the supermarket sale was ending.
What each of them is ranked on
The killer · Saitama · rank 1
Caped Baldy — Hero Association register
Aced every physical test at the certification exam and scored 71 out of a pass mark of 70, which put him at the bottom of the lowest class in the organisation. Punched apart the meteor falling on Z-City, killed the Deep Sea King in one blow in front of the heroes it had already gone through, and met a beam aimed at the Earth's surface with a Serious Punch whose shockwave parted cloud cover across the planet.
statedOne Punch Man · ch. 16, pp. 1-8
The certification exam awards him 71 points against a pass mark of 70 and a C-class designation.
shownOne Punch Man · ch. 16, pp. 1-8
Takes the physical tests at the exam centre in front of examiners and rival candidates.
statedOne Punch Man · ch. 17
Genos, reading the registry, says the two of them have been placed at the lowest rank of S-class and of C-class respectively.
All 11 citations
statedOne Punch Man · ch. 21, pp. 1-4
Genos tells him he has been moved from C-class rank 388 to rank 342.
shownOne Punch Man · ch. 21
Punches through the meteor falling on Z-City and walks away.
shownOne Punch Man · ch. 28
Kills the Deep Sea King with a single blow.
shownOne Punch Man · ch. 36
Repels Boros's Collapsing Star Roaring Cannon with a Serious Punch.
shownOne Punch Man · ch. 36, pp. 54-57 & 62-63
The shockwave off that punch parts the cloud cover across the whole planet.
statedOne Punch Man · ch. 36, pp. 68-69
Boros tells him he had strength to spare and was still holding back.
statedOne Punch Man · ch. 177, p. 37
Is promoted to A-class rank 39 after the Monster Association incident.
statedOne Punch Man · webcomic ch. 96, p. 16
The webcomic gives the same A-class rank 39 placement.
The victim · Carnage Kabuto · rank 12
Broke the left side of Genos's face with one punch, then blew the cyborg's own fire blast back into him to finish his part in the fight — and became the first thing in the series to read Saitama correctly, leaping the width of the room rather than swinging, and asking him where the strength came from. Went into Carnage Mode on hearing the answer, which he took for mockery.
shownOne Punch Man · ch. 10, p. 14
Puts Genos into the tunnel wall, then breaks apart the left side of his face with a single punch.
shownOne Punch Man · ch. 10, pp. 9-20
Blows Genos's own fire blast back into him with his breath, ending the cyborg's part in the fight.
shownOne Punch Man · ch. 10, pp. 25-31
Senses Saitama's strength mid-charge, leaps back across the room, and says he would have died attacking.
All 7 citations
statedOne Punch Man · ch. 11
Announces he will stay in Carnage Mode and rampage until the following Saturday.
shownOne Punch Man · ch. 11, pp. 16-19
Wrecks a great deal of the combat experimentation room in Carnage Mode.
shownOne Punch Man · ch. 11, p. 21
Saitama's punch disintegrates his chest, neck and head.
shownOne Punch Man · webcomic ch. 10-11
The webcomic runs the same fight in the House of Evolution's combat chamber.
What this does not settle
One death in one work. It is the only place the record puts these two in the same room, 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.