The former Newport Gwent Dragons flanker has now conquered the challenge he took on after being forced to retire with a shoulder injury two year's ago.
Parks has now scaled the highest peaks on all seven continents and trekked to the North and South poles all within seven months.
"My energy levels went from a quarter of a tank to pretty much bone dry and the last hour of this summit I had to dig pretty deep," said Parks.
"I was pretty fatigued, my legs were tired and it was quite tough mentally, it was pretty much just a snow plod.
"I feel sort of numb actually, what we have achieved hasn't sunk in yet. I'm not as emotional as when I reached the top of Everest, I can safely say, I didn't shed a tear.
"It'just really hard to put in to words. I'm sure when I'm back home and I've got the team around me we can reflect and I guess it will sink in then.
"I had every confidence I would be able to do it from day one. But with some of the hurdles and the dramas that we've had over the past seven months I'd be lying if I said I hadn't had my doubts.
"Physically I think my body has just about held up, I'm not sure if I've got another mountain in me for at least another couple of months."
Parks amazing adventure was almost derailed after he suffered frost-bite in his right toe after conquering Mount Everest, but the former Pontypridd man battled on to book his place in the record books.
In total Parks has reached the North and South Poles and scaled Mount Vinson, Aconcagua, Kilimanjaro, Carstensz Pyramid and Mount Everest, Mount Denali and Elbrus.
He completed the race, which aims to raise £1m for Marie Curie Care, in six months, 11 days, seven hours and 53 minutes
"To stand on the top of the world's highest mountains and some of the most beautiful places on earth, I'm just so grateful to so many people who have made this 737 Challenge possible for me really.
"I know I've put everyone through the wringer, I'm just grateful to get back in one piece safe and sound and be able to share it with everyone. I'm so grateful who everyone who took a leap of faith in me."
Former Lions captain Gareth Thomas has led the tributes to his former teammate and tweeted: "Congratulations Parksy! You're nuts, but for an amazing cause mate. Hats off to you. Backing you all the way pal."
To sponsor Richard, visit www.justgiving.com/RichardParks737Challenge