Or, to word it differently, what is the largest lead ever lost by an NHL team? If you can, list both in regulation and overtime.
"Nine teams have overcome a five goal deficit to win the game. However, probably the most remarkable of these was the St. Louis Blues on November 29, 2000. Down 5-0 in the thrid period agains the Toronto Maple Leafs, the Blues scored 5 goals in 15:27 and won the game 18 seconds into overtime."
So I'm guessing it's 5 goals for both regulation win and an overtime win.
the only remarkable come-from-behind game I remember is the "Miracle on Manchester" game in the early 80's between the Los Angeles Kings and Wayne Gretzky's Edmonton Oilers in Game 3 of the Smythe Division Semifinals (first round of the playoffs). The Kings were down 5-0 entering the final period. The Kings ended up winning 6-5 in overtime.