@Jating. You cannot compare Pacman and these other boxers on mental strength. If you read the hardships that Pacman has experienced as a small child and a teenager, we can be quite certain that many people who would experience a similar experience would give up already and will grow older poor and hopeless.
On Spence, this is a similar experience as Devin Haney. I reckon the both of them might need a psychiatrist to help them to defeat their mental opponents hehehe. Pacman however, does not need this. If his body has maintained strength, he would not retire.
Oh yes, before we forget, one of them is Devin Haney who seems can't accept his big L against Ryan Garcia and most likely he should seek mental help as well. Probably this is one sport that just one big lost, it will be over for some boxers.
And you are right, and that what separate the elite boxers, like Manny Pacquiao who comes from hardship to other great to good fighters. But when their back is against the wall or have taken a lost in their career, most of them can't come back and as if their career is define already with that one lost in their resume.
It might also be how he grew up and it appears that Pacman was very much loved by his mother and she might have also taught him good values despite living in poverty in his younger age.
I reckon he might be the only boxer who has 8 losses and the fans and promoters are very much interested in his fights hehehe. Other boxers cannot have this type of popularity with 8 losses.
That's what really makes Pacquiao special, it is not not how many losses he has throughout his career, it's how he bring fight fans all together and see his fights and root for him. And the charisma, not everyone has it, but Manny has that factor as well.
We have seen the likes of Floyd, undefeated, but still he might declared himself the best boxer, but there are some boxing experts who put Manny ahead of him in terms of greatness and accomplishment even if Floyd has 0 losses in his career.
And did you know that Manny is rank then number 1 Asian athlete by ESPN in the 21th century?
https://www.espn.com/espn/story/_/id/40632727/top-25-asian-athletes-21st-century1. Manny Pacquiao, boxing
Key accomplishments: Since Jan. 1, 2000: 35-6-2 pro record. Only boxer to hold eight world division titles, held world titles in 2000s, 2010s and 2020s. Plain and simple, "PacMan" is arguably one of the greatest boxers of all time. He won world titles in an unprecedented eight weight divisions, showcasing his versatility and dominance. Pacquiao's career spanned over three decades, during which he defeated numerous boxing legends.
Recognized as Fighter of the Year by Ring Magazine in 2006, 2008, and 2009, he was also named BWAA's Fighter of the Decade for the 2000s and won the Best Fighter ESPY Award in 2009 and 2011. Pacquiao's remarkable achievements and impact on boxing highlight his extraordinary legacy and has now stemmed into a career in politics and as an executive in various sports.