I dunno, being one of those boring sods that wants to win more then he wants a challenge (I play games to relax, so what?) I do wish that two things were done everywhere:
1) Let me pick my difficulty
Yes, even the Dark Souls thing, I'd like that ability. Even if it's just between "Hard" and "Nut-Bustingly Hard", I'd like the choice. Or better still, just let me make the choice on the fly, without even going to the option screen!
One game I really liked about 4 or 5 years ago was Wario Land Shake It. It's a fun little platformer, and if you play just trying to get to the end, it's pretty damn easy. But there's a bunch of little challenges in every level - collect this many coins, don't touch water, don't kill an enemy - and in some cases, completing them is almost annoyingly difficult. But hey, it's my choice. If I feel like breezing through the level, I breeze through it. If I feel like getting that 100% completion more? Well, the nut-kicking awaits.
2) Don't make anything impossible in the wrong circumstances, PLEASE.
Borderlands 2 is an absolute BASTARD for this. I refuse to belive that the Badass Pyre Threshers can be killed as anyone other then Gaige and maybe Axton. In case you don't know: They're able to burrow. When they unburrow, they releace a fire nova AoE attack around them that hits pretty much instantly. They won't unburrow until you're in range, and you can't actualy hit them while they're burrowing. So, in other words, if they burrow, you're taking a hit. End of. And it's a LARGE hit, and if it sets you on fire, you're basically dead. And yes, you CAN get a second wind off of his tentacles, but if the massive fucker decides to get in the way of your aim, you're buggered and have to reset.
And those FUCKING Skeleton Sears, with their ability to just say "No, fuck you, you're not hitting me right now." Which they do. A. LOT.
And I literally spent around 10 minutes fighting ONE enemy, an enemy that had the ability to level itself up FIVE TIMES. Which, in Borderlands 2, basically takes an enemy to "a fairly hard fight," to "You may as well just run around this area for ages getting potshots, because he's going to one shot you." The ONLY reason I managed to beat him at all was because he had only Melee attacks, and even then it was a crapshoot, because his jumping attack became basically undodgeable at a short enough range, and his attacks in general seemed to hit you about 10 foot further then they should. So if you get hit when you shouldn't have, and then get the jumping attack, too bad, you're dead, start again from square 1 of 10,000. And whoever made Treeants produce electrical homing spores on death that can easily send a character who just came up from Fight For Your Life right back again deserves a swift kick up the ass for being an absolute dick-ward.
Playing Borderlands 2 with those enemies inside it is like bashing my head against a brick wall for fun. It just causes pain and a headache. And that isn't fun. I refuse to believe that someone actually play-tested it properly - no-one could go through the crap I did and say "Nope, this is good, release it."