I can think of only one game that the difficulty was the primary reason I did not complete it. Generally, difficulty is just a contributing factor to my not completing a game, usually if I'm just exhausted with the game, there are other things I don't like about it, or I'm more interested in playing something else at that moment.
The only game I ever quit simply because of the difficulty was Men of War. I'm not particularly good at strategy games (real time or turn-based), and I have to be in the right mood to play them. I have only ever finished three RTS's: Halo Wars, Company of Heroes, and Dawn of War. Most of the time, I lose interest in the genre part way through the game and give up. However, Men of War hit all the right notes for me: it didn't require base building, it generally focused on controlling a relatively small number of units overall, and it was based in World War II, a period of history I quite enjoy. I knew going in that it was a difficult game, and I adjusted my expectations accordingly. I might have even finished it if it weren't for one thing: defense segments.
I hated them.
I'm not a fan of them in any RTS simply because I'm not smart enough to know where to place my units for optimal defense, but I can usually blunt force my way through them. I managed it several times in Company of Heroes (and probably Dawn of War, though I don't remember that game as much). However, Men of War's difficulty just would not allow this. I remember getting to one level that required me to defend... well, to be honest, I don't even remember what it was. I think there was a bridge or something? I don't know. I just know that it didn't start well and it got even worse. The bad part about defense levels, too, is that it isn't always obvious that you are going to fail until some time in, and you might have to go back quite some time or even restart the mission to get yourself before a point where the mission was too far gone to win.
I don't fault the game for this, though. Again, I knew what I was getting into. I just didn't have the skill to get through that mission, and I quit because of it. I enjoyed everything up to that point, though, so it was worth the purchase in my book.
I'm sure I could come up with a far greater number of instances in which difficulty was a contributing factor, though. I don't mind difficulty if it's fair and the game interests me enough or is enjoyable enough despite of or because of the difficulty. However, sometimes, the more I play a game, the more the things I might not like begin to come to the forefront, and if high difficulty is place on top of that, I'll usually give up the game. If I enjoy a game enough I'll push through a difficult spot, but if there are too many other things that are annoying me, I won't bother to continue.
This happened with the Bright Lord DLC for Middle Earth: Shadow of Mordor. I enjoyed the game up to a certain point. The combat was pretty fun, the captains and chiefs were challenging in the right ways most of the time, and the game's Nemesis system was fascinating and fun. However, once I passed over the 10 hour mark, little things started getting to me. The sheer number of enemies made traversing the huge, visually-uninteresting world a slog, getting to the captains could be a huge pain in the more densely packed areas, and the stealth was too simple to be much fun after a while. I found myself constantly repeating the same things over and over, and suddenly the little quibbles I had with the combat became more noticeable. By the time I finished the main game, I was a little weary of the formula. However, I was intrigued by the potential story of the Bright Lord DLC, and I was interested to know how the slightly different playstyle required by the different moveset would affect gameplay.
Unfortunately, it was mostly more of the same, except I felt slightly less powerful and much more limited in abilities despite controlling an (supposedly) more powerful character. I finally gave up when I got to one mission that required me to defend two towers or siege weapons or something. The two objects were on opposite sides of a ravine of some sort, and they were under constant attack by Uruks. The key to succeeding was using the power of the One Ring to turn Uruks over to your side and allow them to defend the objects from attacking Uruks. There are only two means to turn the Uruks to your side (that I can remember, anyway): hold a particular button until a meter fills to turn a single Uruk; or use a special AOE attack that can only be performed once a meter has been filled, and that meter is only filled by attack or killing enemies. The problem with the former method is that your character is not immune to attacks while trying to turn an enemy, so if you get interrupted by an enemy attack (which you most likely will) you'll have to restart the process. Even if you can pick up from where you left off, it still takes time, which is a precious resource in this mission because if the defended objects are destroyed, you fail the mission and have to start over. The problem with the second method is that it's hard to find a reliable way to build up the meter without killing all the attacking Uruks, and even once you do get it built up, the AOE has a limited range. If you use it without many Uruks being nearby, it wastes a useful means of getting allies to defend the weapons.
And they are necessary for this because you can't be at two places at once. I just found this unnecessarily difficult, and it highlighted all the things I didn't like about the game's combat. So while the difficulty itself was not the reason I quit the game, it definitely contributed.
I could probably think of more examples, but I fear I've already made this post too long, so I shall refrain.
Post edited September 27, 2019 by Daedalus1138