What is the worst combination in Texas Hold'em?

I always thought the worst combination was 2 7 variegated. But recently we played at my friend's house and for company taught his girlfriend the rules. At the end of the tournament we were left alone with her with the same stacks. I got 66, she takes my all-in and catches a seven. I came home, looked at the calculator and saw that the probability of not losing was 28%. For example, 23 different suits have 15%. I think that when playing in limit hold or with a lot of limpers in unlimited 2.3 will be better. Your opinion?

Probably JJ)