The worst Texas Hold Em poker hands are, invariably, the hands that you have to stick with to the last community card, playing all of your chips just to lose to the last community card, and thus losing all of your chips and your seat at the table (if playing in a tournament with no re-buys). Hands like this are not readily definable, and are referred to as “bad beat hands”. An example of this would be if you started with the King of hearts (Kh) and the Queen of hearts (Qh), had three hearts show up on the flop, and lose to an Ace of hearts (Ah) and a deuce of hearts (2h). But bad hands to start the game off, pre-flop (the flop is the three initial cards that the dealer plays face-up on the table for all players to use with their 2 hole cards), are cards that are non-suited (two cards of different suits, like a heart and a spade), and have more than 3 cards separating them (Q-7, K-8, or the worst of them all, the 7-2, all off-suited, negating the possibility of a straight or a flush probability off of the flop).
Texas Hold Em is a very hard game to win at, as lady luck can shine on any two cards that play the flop (the players that pay the amount needed to see the flop, but with lousy starting cards). There are a lot of people who will play any two cards at times, and get lucky with three of a kind, or even a full house off of the flop, as any three cards in the deck can show up on the flop. On paper, a pair of Aces is the best hand to start with, but if three 7′s show up on the flop, the pair of aces will no longer be any good against even the worst of all starting hand, the 7-2 off-suit. A lot of poker players play a style that is called “bingo”, in that they play any two cards, hoping for a flop that gives them the best possible hand on the table. These players will usually either lose out right at the start, or make a few lucky hands before being kicked out of the tournament, or off of the table, with superior cards and a co-operative flop.
Small pairs in Texas Hold Em can be a real stack blower (take most of your chips away from you), insofar that they invariably lose to a higher pair, or a pair of highly rated starting cards, like A-K. Pairs under 7 are considered “suicide pairs”, because you need one of those cards to show up on the flop, where there are only two more of those cards in the entire deck (other players may have your other two cards as well). When someone plays poor hands before the flop, they are considered to be “fishing” for a hand. As the only way for them to win the hand is to match the face value of their cards, with no straight or flush possibilities on the flop. Playing tight (only playing good cards, except maybe when you are the position player.
The worst Texas Hold Em poker cards are the two cards that are your last hand, as they take away all of your chips and have the winner of the hand rake in all of your chips while you get read to leave. Nobody plays to lose, but many people play unorthodox styles, which then makes the adage that “any two hole cards can win” come true.