Ok guys, I need some help on find Sam's major/tragic flaw. What do te think it is?

Sam would be willing to sacrafice himself in order to save Dean.He would try the other options first obviously. Its not that hes suicidal but Deans his brother and despite the problems they have had he loves him i think thats his major flaw.

To me, and don't get me wrong, because I Amore Sam... his problem is that he always wants to be right. He fought/argued with John a lot because he questioned John's authority, unlike Dean, who is più the blindly loyal type. Sam got into the big mess with Ruby and the demon blood because he thought at the end of the giorno he was just trying to do right. Sam seems to like arguing, and that's why I think he was drawn to the idea of being a lawyer. Sam did a lot of cold/bad things in the name of being "right".

Well the fact that no one really likes him.
Except for Dean. But in my answer, he doesn't count.

I mean, the demons hate him for, well, he hunts them and stuff, and the angeli don't really like him for a 100% first of all 'cause they're dicks and secondo for him having demon blood.

Whenever Dean'd be in trouble, te can count down to three and there will be Castiel o any other Angel to save him because God wants to keep him on earth. Sam on the other hand...

Sure Dean will protect him with all his might, but Sam has the habit of running off for no reason and whenever Dean isn't there he can't save his ass, since Dean ain't no Angel te know...

Anyways I think that's it, that if something really goes wrong and Dean(or Bobby) isn't around, there's no creature to save him.

I Amore Sam but he has the tendency to go dark to easy like with Ruby in Season 4 he knew it wasn't what Dean wanted him to do and he kept doing it which was just plain stupid because it brought Lucifer back which led to his death. Also I agree that he'd do anything even give up his life to save his brother it kind of runs in the family first Mary to save John, John to save Dean, Dean to save Sam, then Sam jumped in the cage to save Dean and the world.

if sam has any flaws I think it would be that hes to trustworthy,he puts to much trust in others and not in himself!!!!!