This is by far the worst beat I have ever seen and possibly will ever see. In a cash game with about 75% of his bankroll, my buddy had pocket KK, raises triple bb and gets called by the sb (bb folds). the flop comes K K 4. My friend slow plays it, min bets and gets raised all in. Thinking he is about to nearly double his bankroll, he calls immediatly. Showing his KK he sees that the other player has AA.
He has quads, there is no way he can lose right...? Except to quad Aces.
The turn and the river are the two remaining aces, and he loses the immense pot. We ran the odds
that this could happen and found out that, after the flop, my friend had a 99.9% chance to win the pot.