I don't think anyone has bitten their nails as hard as the people who played in this match.
Like other MOBAs, the goal in Heroes of the Storm is to take out the opposing team's base -- one building specifically, known simple as the "core". A match ends when the health bar for one team's core has been reduced to zero. In an impossibly tense match captured recently by YouTuber ZxcAb (via Reddit), one team manages to fight their way back from having their core beaten down to one per cent health. The red team was so sure they had it in the bag that LiLi -- a character known for her healing abilities more than anything else -- tried running in again after all her comrades died to try and knock off that last unit of health.
One per cent! That's as close as one can get to the brink of defeat in Heroes of the Storm before they get shoved off. I'm pretty sure I would have had a heart attack if this happened in one of my games.