La-Mulana was great. Maybe not for everyone. It's loaded with puzzles.
ExtraMedicated
I vaguly remember playing some version (I think a demo) of this in the 90's. Crazy to see it's still going. It's on Steam. I should probably check it out again sometime.
If you'd like a less serious, funny comedy-horror game, I enjoyed The Upturned.
Some less silly games I'd also reccomend are 10 Dead Doves
and
Withering Rooms
I haven't played this yet, so I don't know anything about what difficulty settings it may or may not have But in general, I see difficulty settings as an accessibility feature.
I liked the way that Ender Magnolia did it, where, at a save point, you could adjust several settings to customize the difficulty. I was able to temporarily make it slightly easier just for a few bosses that I lost my patience for.
(On my wishlist for years)
Well now I don't feel like playing it.
La-Mulana would have to be one of my top picks. With the catchy music, the "fuck you" difficulty, and the classic adventure theme really makes it stand out in my mind.
It looks like there are a few games I was slightly interested in trying at some point, but not enough to buy them, but having so many together as a single purchase, I couldn't resist. I even paid the default price of $20 instead of $10.
Shadow of the Collossus
I don't remember if it was on sale, but I got 10 Dead Doves on a whim and I'm not dissapointed so far.
Yeah... It's pretty brutal. I needed to consult a walkthrough even for subsequent playthroughs.