2 and 7. Offsuit 2 and 7 is the worst poker hand you can get. It's so notorious that it has many names, devil's hand, screwdriver, and many more. It's backed by statistics that 2 and 7 offsuit players have chances to win in a game of eight players at 5.4%.
Because it is the lowest ranked four gap hand you can have. It needs help to make a straight, it's a terrible baby flush, and the pairs it makes do not hold up well.