It's got to be one of the more recent ones. I don't remember any FPS from early 2000's and late 90's being a particularly depressing, mind-killing, life-threatening experience, even though there are some "pretty" bad ones there too. Some painful ones:
Delta Force Black Hawk Down Team Sabre : Playing this game is more agonizing than sleeping on a bed full of broken glass. It's unbelievably broken, and beating the other campaign (the possible one) requires the player to not care too much about living. I actually did beat the other campaing, which I consider somehow disturbing. Go read my review.
OF - Dragon Rising : Don't worry, I only payed 15 for this. And my playing experience was worth less than five cents. I played it for 20 minutes (or less), died once, took it out and threw it on the floor. The funny part is, I haven't touched the thing since it, it's still there. And it's a long time.
Team Fortress Classic : What?
Halo Reach : I did like ODST, as my first (and definitely last) Halo game (read my review). So why did I hate this? BECAUSE IT'S THE SAME GAME. Sorry fellas, you really need to try harder. Waste of nature's resources.
The Sum of All Fears : I have completed it, but the controls are horrible and the game just doesn't work.
Timesplitters 2 : First mission is fantastic, ok? Everything else: Please leave the room, my head is about to explode.
I have played many more extremely horrible games, but that is it for now, my mind is not capable of remembering more right now.