Is that the warehouse one?I'd probably say some of the silent heist achievements from Payday 2 would be things I am happy to have obtained, in particular if I was able to do them solo.
Like the gold heist mission, where you can get some money, or ALL THE MONEY, but it's a slow, tedious, nail biting thing, where you can be caught at multiple stages, all by one slip up as you move bag after bag to the extraction point. There is no achievement for doing them solo that I recall, but a lot of the silent heists are totally doable by yourself, if you know what you are doing. And the tricksy sneak-thief in me always gets a warm fuzzy when I pull them off.
My friends and I kept going back to that one. It was fun