I have to say the worst I've played was Crystal Key, twice. First time was after initial purchase, and I stopped playing when it got so confusing what had to be done.
Second time, and I finished it this time, I just had read something about the game and decided to try again. Had to use a WT most of the time because there wasn't any way to know what had to be done when or with what.
If something gets your goat, it just proves you have a goat to get.