What are the "great injustices of chess"? Edmar Mednis stated that in KNN vs K endgame, the inability to force checkmate is "one of the great injustices of chess". The phrase "one of" seems to indicate there are other injustices in his mind.

So, what are other great injustices of chess?
It is probably not only about position, but how about playing for 7 hours, and you are positionally killing your opponent, and you slip up, throwing away all that work?

Here are a couple positions that still probably qualify:

 [FEN "7k/7P/8/6K1/4B3/8/8/8 w - - 0 1"]


You would think that white should be able to win, but no.

Or black here.

 [FEN "6K1/5P2/6q1/8/8/8/1k6/8 w - - 0 1"]

 1. Kh8=