2012 before Game 6 vs Boston the Heat were down in the series facing elimination after losing the 2011 finals .....

man I remember people talking about blowing up the team saying it was over, SAS (along with a lot of others) picked Boston to win the series at that point saying the Heat were done. If they had of lost that game I don't know if LeBron would or could have ever recovered mentally basketball wise.
That game alone was the BIGGEST of Lebron's career. It may not seem like it now but think back if he lost he would have been ringless LeBron losing back to back years with the Miami Heat "superstar" team after bolting from Cleveland. At least now any failures he has atleast he has rings.
Then the way he played that game showed there was NO WAY that man was losing that game he knew his basketball legacy depended on it.