I guess Usopp will win the poll .. if the poll would be "who's backstory was the least sad .... So strong opinions.. first time a whole thread agrees to a point made

...
However, I would like to put up a case for Usopp ...
I think given Usopp's ability, as he was not a DF user or good with swords or cooking or was not a burglar or navigator ... He was left alone by his father with a dying mother who he couldn't help ... I think we all have been in a situation where we want to do things but felt helpless and that makes his story sad for me ... His stories of his bravery was the only thing he had .. a person made of lies , no one loves to lie to save his ass... and finally he recognized it and played it just to survive , initial arcs he was all about that ... He never knew he had the innate ability of snipping which he figured pretty later in his life and now see where he is
About the Water Seven arc, he knew everyone loved merry ... but merry was gift from the special person and crew made little sad faces and said we have to move on ... No one tried enough to calm him down ... little efforts is all I have seen, and considering Usopp was emotionally weak with a weak will ass well (pretty good build up by oda) it was totally a genuine breakdown of him ... He thought it as his failure because he always kept repairing the ship ... HE FELT RESPONSIBLE RATHER THAN HURT AND SO HE HAS SHOWN HIS ANGER BY LEAVING THE CREW ...but actually he only left because he knew he is the weak link of the crew ...
I guess everyone remember when he said that "Merry is our Nakama, will you just leave back your nakama when he will be of no use to you" .. there he was not talking about merry but he was worried about himself as well ... Moreover if Merry wouldn't have been at Enies lobby to save everyone ... Merry wouldn't have gotten the funeral she deserved ... "sob sob" ... She was there in the junkyard ready to be left behind by SHs ...
Someone said that he only saw a ghost trying to repair and there was no reason for him to believe it was merry ... He had feelings towards Merry which was closest to his heart ... Luffy left Merry (may be with a heavy heart but he left) to Usopp and walked away talks a lot about the comparison of feelings of Usopp towards merry vs crew's feelings towards merry ,,,
He was being childish you say ... He was child from heart,,, he was portrayed as the most immature guy in the crew , his character was made like that by oda ... and oda did a brilliant job for Usopp ... Though he messed up the character a little bit after 2 years time skip with Usopp initially abandoning the dwarves and I seriously didn't like it ... I guess Oda felt the same to introduce sugar once again in the picture and make Usopp hero again (the flow of story would have been fine without that and Usopp's haki oda could have shown later in the story, that was not required until he downplayed the character during dwarves attack on factory)....