Going old school on this one: The Hitchhikers Guide to the Galaxy text adventure from Infocom. Got all 400 possible points before you could look up a walkthrough online. Ask someone who has played it how you get the Babel fish and you’ll understand what an accomplishment this was.
Yes, and they released a new edition that runs on Windows 7 and higher.
I believe I saw they released a third game in that series. Yep, it’s called the 13th Doll.
I played the NES port, re-ported to Nintendo Switch. (It was free for a while last year)
I definitely would have run out of money at an arcade.
~Max
The BBC released a 30th anniversary edition of the game online.
I remember finishing Adventure back in my salad days. Don’t remember what happened when I did, though.
For me probably “FTL: Faster Than Light”. It’s a great game but being a rogue-like you die, you start over. And you will die…a lot.
I got pretty good at the game. I understood the mechanics and strategies, watched many videos on how to play and whatnot…and it still kicked my ass even when I would swear I did everything right.
As much as I liked FTL I can’t bring myself to play the company’s other game, “Into the Breach”. It’s got great reviews but I can’t go through that again.
I’ll similarly go old-school with Ultima IV: Quest of the Avatar. It’s a difficult enough game to finish even if you [I]do/I] have access to the internet, and I don’t know how anyone could have possibly finished it back in 1985. I compensated for this advantage by playing through the game with the Shepherd as my main character just to make it that much more hair-pullingly difficult in the early game.
I remember the hint book came with a special pen you used to show the hints … except the one my computer class had was donated and you could see where the original owner lost the marker that came with it and tried to use different ones to varying degrees of success
That’s how I discovered Bulletin Board Systems (BBS).
It was a different time…I miss them.
That’s another game where I remember it being a long game, but I don’t remember any especially hard parts.
I remember getting stuck on Hitchhiker’s Guide to the Galaxy and never being able to progress beyond a certain point.
Does it have dead ends? King’s Quest IV had dead ends, where the game would let you keep playing for an hour or more, only to learn that awhile back…your shovel broke and there is no way to get a new one or continue.
Halo II was the hardest for me.
Yes, notoriously there is one item you have to pick up at the very beginning of the game, otherwise you lose later on.
Was going to say the same thing. Yowza, that was a tricky one to finish. Learning how to get tea and no tea was a particular challenge.
If we are going old school, I finished Super Mario Bros. I also finished the Legend Of Zelda. I was so surprised when I beat the boss!
A really difficult question to answer. I can’t remember the difficulty of games I’ve finished. I tend to either not finish a game because I get to some bit that is either boring or too difficult or I finish them and they seem easy enough with some difficult bits maybe.
Re SabreWulfe And Underworld
I thought both games had been released early and due to bugs couldn’t be won.
Re Battletoads
I had an easier time getting to one of the portals than most. In one of the hoverbike sequences, you need to intentionally ram into an obstacle. This was late in the sequence, by which time things were going so fast I could never avoid that rock.
I will often play games under some artificial, more challenging, constraints. I like stealth games, and often try to play them without killing anyone. Modern games will even give you an Achievement for it. For example, I’ve completed Deus Ex, Deus Ex: Human Revolution, Dishonored, and Mark of the Ninja in this manner.
Well, aside from a few rooms in the Stygian Abyss, the combat is more frustrating and time-consuming than it is difficult (as long as you don’t get ambushed in your sleep or run out of food or reagants or let your healer die.)
The puzzles, though? I don’t know how anyone independently figured out in 1985 that you have to go down a staircase behind Lord British’s castle, descend to the eighth level of Dungeon Hythloth, fight your way back up to level one via a different path, exit in a single-tiled spot on the other side of Britannia, appropriate (not steal, of course, because that wouldn’t be very Honest of you) the hot air balloon you find there, and use the Wind Change spell to navigate to a space a single tile wide surrounded on all sides by mountains and invisible from the rest of the map in order to dig up the Stone of Spirituality.
I mean, I had access to the internet and it still wasn’t easy to figure out.
Released early? Not on the spectrum, don’t know about ports to other systems - Ultimate were meticulous, you could complete all their games. Your reward was the most anticlimactic gaming experience ever, a minimal effort text screen basically saying Well Done mate 
Sabre Wulf was fantastic and Underwurlde was not, in hindsight, it just felt epic because it was so labyrinthine and difficult. But their GoaT title was the next one, Knight Lore - that was a landmark for isometric gaming. They actually had it done before the first two but sat on it for a full year, as it would have buried the earlier games.
The guys behind Ultimate - the Stamper brothers, went onto become major figures in gaming - they founded Rare and were the first western developer for Nintendo.