My own team's parents. I had to miss the game due to another commitment, and it happened to be a playoff game that would take us to the championship. My asst coach, who has been coaching basketball for at least 10 more years than me, got yelled at multiple times for his decisions during the game from my kids' parents. At one point, when his own son was having issues (has some learning disabilities), a parent started yelling at my asst coach to "take his baby son of the court and let the real men play." By real mean, he was referring to his 8 year old son.

Baseball parents in our league aren't that bad. Football can get bad, but luckily we win enough to satisfy even the most vocal complainers.