Easily blowing all other bets well out of the water:
Bitcoin difficulty at or above 2B before Feb 2014.
That's 1868 BTC and change paid out over 99 winners, out of 123 bets. Bitcoin's largest settled bet to date, and quite possibly the largest in all of prop betting.
This'd also be
one of those cases where what initially looked like a longshot ended up a nail-biter. And one of those proofs that BTC's betting is decidedly happening on BitBet.
Congrats to the winners.