The flanker was an inexorable threat in Dublin and was named man of the match following a performance in which he overwhelmed Wales' Sam Warburton.
The visitors succumbed to a brutal 26-3 defeat. It would be the result of O'Mahony's controlled aggression and powerful intent; the 24-year-old Munster captain spearheading his side's display against a Welsh team which looked completely caught out.
Such intensity had been incubated in training sessions which O'Mahony later referred to as "savage" and that provided the Irish with the mental edge vital to seize victory.
"A lot of that has to go down to the fight and the want that we showed," said O'Mahony. "At the end of the day we wanted it more than they did, that was evident. I don't think the scoreline flattered us, but we fought for everything.
"That is where we need to be at, we need to be fighting for every 50-50 ball, everything that goes on the ground. They are the ones that make the difference."
Chris Henry and Paddy Jackson both claimed first international tries as Ireland dominated with their driving maul. O'Mahony praised John Plumtree, Ireland's forwards coach, for implementing the new methods which elevated his side's driving game to new heights during consecutive Six Nations wins.
The flanker also gave credit to captain Paul O'Connell and hooker Rory Best, for their endless hours of analysis and meticulous tinkering in the line-out. "These guys spent an awesome amount of time on laptops and a savage amount of work. Credit has to go to all of them," said O'Mahony.
Ireland will now chase the Triple Crown when they face England at Twickenham on February 22. It is the sort of challenge to which Wales had been accustomed as they collected four Six Nations titles - including three Grand Slams - and a World Cup semi-final appearance during the past nine years.
That has seemed more like a lifetime ago in this Six Nations, though, with the team reeling on the ropes and clinging to dreams of further silverware, rather than setting the title pace.
Their haunted expressions in Dublin told their own story as the players struggled to comprehend how far they have fallen. "We have got two weeks to prepare for France and that game is going to really show our character and how we bounce back as a squad," said Alex Cuthbert, the Wales wing.
"Fair play to Ireland. From minute one, they turned up and were ruthless in what they did. Last year, it was a game of two halves [against Ireland]. We kept going up and up in the second half, but on this occasion we couldn't click as a team.
"I haven't had many of these losses. I've had losses from last-minute kicks and stuff, but this is completely different when you haven't been in charge of the game from minute one. Maybe a couple of 50-50s didn't go our way but we weren't at the races, and they were from minute one to minute 80. We couldn't get into the game.
"It is going to feel like a long week this week. We have got a lot of things to get right, but we've got a lot of time to get them right, which is good. Physically, we are in peak shape, I think it is more mentally."