A real one. So I'm not including obvious answer like Bushland (that game is also known by another game, it's where you're drawing squares with chalk and nothing else), or that one "game" that's actually merely a storybook that someone made you do when you were 10.
The worst ACTUAL game I've ever played is Half-Life. All if the reasons that people say "made it amazing", and all of the reasons that people say make Half-Life 2 bad as compared to Half-Life 1 (those people are there, yes just look), are in fact present in Half-Life 1 and make it terrible. The most boring game ever played. It has no story yet unfortunately and thank fully unusually for the time, is a game which actually requires an amazing sorry to be worth it. Although we here that a lartially-decent story eventually emerges, that happens for a small but in the very last level of the game. It has "puzzles" which really do not belong in a FPS at least not in every single section of the game, and requires jumping which also should be banned from any FPS because you can't see your jump to know where you are going. The default key mapping is also terrible. The very worst thing about this game is that it ushered in the "CoD era" where every game released for several years is either military ugliness, a franchise sequel, or completely unpromoted. It's basically like Half-Life invented the Xbox.
Of course this also obviously means that I have not yet played Half-Life 2, but since that story actually DOES have legitimate things happen in it it most definitely be at least marginally better then this incredibly boring Half-Life 1!
Edited by God on February 18, 2018 at 20:58:58