2003 - No. 8 seeded Magic blow series 3-1 lead to No. 1 Pistons
2009 - No. 2 seeded Celtics fail to close out series 3-2 lead to Magic
2010 - Celtics lose both Games 6 and 7 in NBA Finals to Lakers.
2012 - No. 4 seeded Celtics lose Games 6 and 7 of ECF to LeBron James and Miami
2015 - Clippers fail to close out v. Houston with 3-2 series lead.
2016 - Clippers take 2-0 lead in first round, then lost next four to Portland
2020 - Clippers blow 3-1 series lead to Denver Nuggets
Extenuating circumstances in several situations. The 2003 Magic get credit for having Detroit on the ropes, but lost Games 5, 6 and 7 decisively. Games 6 and 7 of the 2010 NBA Finals were in Los Angeles, Game 7 a 83-79 decision. 2012 against Team LeBron (James/Bosh/Wade) was another tough out.
But failing to close out the Nuggets as the pro basketball world had been anticipating a "Battle for LA" conference finals for months will sting for a while.