Many games have achievements and they offer players incentives, goals, and alternative ways to play through the game. Unfortunately, this doesn't always go off without a hitch. In some cases a player can be persuing an achievement and have no way to know if they are actually succeeding. When the player finally gets to the end and feels like they should get their achievement it may not register. If the achievement was something the player has been working on for the whole game they will feel cheated.
The game Dishonored has two notorious achievements. One is called Clean Hands. In order to get it, you not only have to play through the entire game from start to finish without killing anyone, you also have to keep them from getting killed. If you sleep someone and they fall off a roof, you lose the achievement. If they get attacked by a swarm of rats while they are unconcious, you lose the achievement. There's a tracker at the end of each level that tells you if you succeeded but it is unreliable. I have a complete play through of the game with 0 deaths at the end of every level and was meticulous about keeping unconcious enemies safe. At the end, no achievement. The other achievement is called Ghost. For this you have to never be seen from the start of the game to the end. Again there is a tracker at the end of each level and again I have a checkmark next to never being seen. Again, I got no achievement. I feel extremely cheated to have gone through the whole game with never being seen and never killing anyone only to be denied the payoff.