I quit playing the Batman Arkham games towards the end of them because they were too annoying to play due to artificial difficulty inflation. I enjoyed the combat and the puzzles, but by the end of the game, they ran out of unique enemies and challenge and just started throwing you in rooms of such diverse enemies that have immunities that make it just a fucking chore to play. This guy is immune to counters, this guy is immune to grabs, this dude is immune to light attacks, this dude has to be grappled, this dude will aggressively follow you and interrupt all the special moves required to take out the twenty other guys in the room. Its just a chore. Its not 'too hard' its just a chore and a slog and adds nothing to the experience.
Also on the subject of artificial difficulty inflation, I also hate when all the difficulty slider does is make you have less health and enemies have more health or any similar system. It is lazy and bad game design, and is essentially the dev saying "we have no creativity and AI coding is hard so here's a sponge that does one million damage by just looking at you cupcake". See also games with "The Rubberband Effect" where the lazy devs just let the AI outright break the rules as opposed to even attempting to have a balanced challenge.
And finally, on different gear, I hate when single player games patch out exploits that are not something that would be accidentally done in normal gameplay. They always say its for balance, but at the end of the day the player gets to choose whether or not they use said exploit and the people that do not want to can choose to just not do it. This has become even worse in the current "Patch Culture" of gaming, and also seems to be in proportion to the death of cheat codes as well. I will never understand why Bethesda would utilize time and resources to patch out exploits in a game while the same game-breaking bugs stay in sometimes forever. Its single-player, why are you worried more about people choosing to exploit the game that they bought rather than fixing the bugs that prevent others from playing?