(CNN) He came from the streets. He came from nothing.

After his father abandoned him at the age of five, boxing great Roberto Duran was forced to start earning money by going out and shining shoes rather than attending school. He gave the money to his mother and family, because they needed it more than he did.

"Survival and pain can be a great motivator," Mat Hodgson -- the director of a new documentary about Duran, who came from the streets of Panama and became one of the fiercest fighters of all time -- told CNN Sport.

"Boxing would have suited Roberto -- it is quite primal, but certainly those circumstances he's come from provide a pure motivation to escape."

If he had to fight for survival from the very outset, Duran's early life also provided the perfect apprenticeship for a life using his fists professionally.

"After the childhood I had, who the f*** was I going to be scared of?" Duran wrote in his autobiography in 2016.

"Boxing champions never come from rich neighborhoods. They come from the barrios -- the gutters -- it's God's law."

I Am Duran follows the path of the Panamanian's career in the 20th century, all the highs and all the inevitable lows -- and the moment that Duran still can't seem to escape to this day.

Almost 40 years ago, he locked horns with America's golden boy, Sugar Ray Leonard, in New Orleans. Duran was humiliated. And the bout infamously ended in him quitting and apparently saying "no más" -- Spanish for no more.

It was one of the most iconic fights in boxing history and a defining moment in Duran's life and career.

The 'Tasmanian Devil' with 'hands of stone'

"He was fearless," says Hodgson of Duran, who picked up the moniker "Hands of Stone" during a career that spanned five decades.

"Fighters would take one look at me and then crap in their pants," Duran wrote in 2016. "In a lot of ways, I was Mike Tyson before Mike Tyson came along," he continued, referring to the former world heavyweight champion.

At one point Duran's record stood at 71 wins and one loss. Opponents who faced up to him in the ring spoke about a "look in his eyes" that was "absolutely terrifying," says Hodgson.

Outside of the ring Duran's life was similarly eventful. According to his autobiography, Duran even "died for 30 seconds" on the operating table following a bad car crash in Buenos Aires.

By fighting his way out of poverty and establishing himself as one of the world's greatest boxers, Duran became the poster child of Panama. His triumphs and struggles also became synonymous with the triumphs and struggles of Panama.

I Am Duran not only follows the career ups and downs of the boxer but is also a unique glance at Panama's history in the 20th century -- be it the Panama Canal, US influence in the region or the various political upheavals that dogged the country.

"Sport is a great wormhole into other areas of life," says Hodgson, as he reflects on the fluxes of Duran's career and life that almost seem to follow the same curve as Panama's.

"Duran's history is almost as big as Panama itself," adds the director.

No más is the 'elephant in the room'

However, it's that "no más" moment which arguably overshadows everything else in Duran's career.

"Roberto regrets it so much now ... it annoys him just to hear those two words," says Hodgson.

I am Duran pivots around the long term rivalry between the Panamian and Leonard. A rivalry, which Hodgson refers to as the "perfect storm."

The pair first came up against each other in Montreal, Canada in 1980 -- dubbed "The Brawl in Montreal."

Sugar Ray was America's darling, who had an Olympic gold to his name and was getting paid five times the amount Duran was for the fight, according to Hodgson.

'Sugar Ray was caught off guard and wasn't ready for this kind of Tasmanian Devil who came into the mix," Hodgson said.

The boxing world was stunned by Duran's victory and just five months later a rematch was scheduled.

Much has been made about Duran not being prepared for the second bout. Buoyed by the first victory, he had spent a lot of time celebrating, partying and not a great deal of time training, according to the documentary.

Leonard changed his tactics and came back more mentally and physically prepared.

Footage shows Leonard actively toying with Duran during the fight -- up to the point where Duran calls time on the fight in round eight and supposedly says "no más" to the referee.

The backlash from that moment has haunted Duran. How could a man who had made a career from never giving up, have given up? The boxing idol was even shunned and ostracized within Panama itself.

"Roberto Duran still doesn't really know what happened that night ... it is the elephant in the room," according to Hodgson.

Although they couldn't get Duran to confirm whether he said "no más," Hodgson says his actions are very revealing and will help us "read between the lines of what happened."

"Roberto can't get away from the no más moment, he can't bluff his way out of no más. I think that's why he physically gets so agitated in the documentary," Hodgson says.

A story of 'hope and inspiration'

If recollecting the "no más" incident still agitates Duran, it was also the making of him, according to Hodgson.

"I believe it made him more loved in the long run," Hodgson says. "It made his comeback even greater -- it made him more human to everybody as well. So as much as it annoys him it sort of made him as well."

Hodgson believes the film is one of "hope" and "inspiration" that teaches us a lot about what cultural icons can do for countries.

Duran gave Panamanians hope in moments of crisis and a sense of value, where they hadn't felt valued before.

I am Duran also gives us a glance into a boxing world of an older vintage -- often perceived as a harder and more entertaining spectacle.

Ironically, this is another topic Duran and Sugar Ray Leonard verbally spar about today.

In a joint interview to promote the documentary, Leonard described the sport as being "healthy" and "not dead like some say it is."

Duran said he had "no respect" for the current crop of fighters.

"We were born in the time period of the real fighters," he said.