Already a winner over 100m earlier in the week, Peaty came home in 25.99 seconds -- 0.53sec ahead of his nearest rival -- and just 0.04sec short of the world record time he set in Tuesday's semifinals.
Brazil's Joao Gomes Junior took silver, while South Africa's Cameron van der Burgh claimed bronze.
"I think I have to retire and give it a few years and come back when he's older," the 29-year-old Van der Burgh told reporters.
"It's really impressive," added the South African swimmer. "It's not even breaststroke anymore, he's swimming like a new kind of stroke, like a metamorphosis between (butter)fly and breast."
It's a stroke that enabled the 22-year-old Briton on Tuesday to break the world record twice in a day, becoming the first person to go under 26 seconds as he clocked 25.95 secs to reach the final.
Out on his own
The worry for Peaty's rivals is that the Briton just keeps getting better and better.
He made such waves at the Rio Olympics
, that Michael Phelps -- the most decorated swimmer of all time -- was opened mouthed at his world record-breaking performance in the 100m breaststroke.
"It's one of the grossest swims I've ever seen. I'm just glad I don't have to race him," said the American, the owner of 23 Olympic gold medals.
Peaty has some way to go to match Phelps' achievements, but the Englishman has made no secret of his desire to be the Phelps
of the breaststroke.
In the final of the 100 meters in Rio, Peaty won by 1.56 seconds in a race often decided by a fingertip. A mere second separated the remaining seven swimmers in the final.
Five-time Olympian Mark Foster believes his fellow Briton is so good, he will remain a dominant force in the pool until he decides to hang up his swimming goggles.
"As long as he stays fit and injury free, I can't see anyone touching him until he retires," Foster told CNN ahead of the FINA World Aquatics Championships in Budapest. "He's that good.
'A bit of a freak'
It was during London 2012 that Peaty and his coach Mel Marshall, who by then had been teaching the swimmer for three years, devised a plan to ensure he would be the best in the world in four years' time.
For Foster, he argues the talent was always there but the hard work was the missing ingredient.
"He's obviously physiologically gifted," adds the former world champion. "He's not a coordinated athlete necessarily, but breaststroke was just what he was born to do and he works incredibly hard at it."
At 1.91 meters and with a monstrous wing span, Peaty is the perfect shape for elite breaststroke.
But he stands out because of what he does underneath the surface.
At major championships, he has grown accustomed to rival coaches following his every stroke from pool side. His body becomes an almost inverted bend from shin and knee, which he calls "a hyperextension of sorts."
He jokingly describes himself as "a bit of a freak," but his performances are other worldly and no one has even got within 1.3 seconds of his best 100m time. No small feat in an event which lasts 57 seconds.
'Who works hardest wins'
Peaty might not have broken his 100m breakstroke world record in Monday's final at the ongoing World Aquatics Championships, but he easily retained his title.
In comparing Peaty with Ed Moses -- the 400m hurdler who won 107 consecutive finals between 1987 and 1997 -- Foster prophetically told CNN before the championships: "He'll win and he'll be quick, and he'll continue to make this his event. It's a bit like Ed Moses, really."
Peaty does not lack confidence but it stops short of arrogance.
"My coach wouldn't let me get arrogant nor my family -- Mel shoots me down every day," he explains.
He likes to downplay his achievements in the pool by saying "I'm no good at anything else," but Britain's first medalist of the Rio Games can also talk for Britain.
In the immediate aftermath of Rio -- Team GB's most successful ever Olympics with a total of 67 medals -- people would congregate outside Peaty's family home, hoping to get a glimpse of the world record holder. He has since moved out, having bought a home of his own.
"The hardest thing was adjusting to what I'd done," he says of the post-Rio haze, in which he took two months off and embraced his penchant for eating burgers.
But despite having achieved the long-burning ambition of Olympic gold, he insists he is as motivated as ever.
"It's who works the hardest that wins," he says, downplaying his natural talent and freakish leg kicks. "You see people fall off after a Games, but that won't be the case for me. I think I can do it again."