I'm just wondering what dungeons in Western RPGs are most infamous for being bad, frustrating, unfair, or just generally awful dungeons.

A couple criteria:
* The dungeon needs to be from a game that's recognizably a WRPG, not a JRPG, and not a roguelike. (So, Dragon Quest 2's Cave to Rhone, as infamous as that dungeon is, would not qualify because it's from a JRPG.)
* The dungeon should not be that I call a "megadungeon", though a significant portion of such a megadungeon could qualify as a dungeon in its own right. (A "megadungeon" is one that takes up the majority of the game or close to it. Wizardry 1's dungeon would be an example of this, as would be the one that makes up the entirety of Ultima Underworld. Something like Baldur's Gate 2's Spellhold would not be a megadungeon, as it's only one chapter of a game that has something like 7 or 8 chapters (and Irenicus's Dungeon wouldn't be a megadungeon either).)

The idea for this topic came because I heard about the final dungeon in Pathfinder: Kingmaker, and how obnoxious and unfair that dungeon is, and, as I lack experience with (non-ancient) WRPGs, I'm wondering what other notorious dungeons have shown up in WRPGs.

Edit: Why the low rating?

The ones in Arcanum are really terrible, especially an early obligatory one (some dwarven clan mines or whatever). Long, tedious, without any interesting content, just combat after combat against enemies, some of whom have annoying abilities like breaking your weapons etc. Horrible design.

Most of Daggerfall's (procedurally generated) dungeons come to mind. The terrible 3D map(s) didn't help.
I still liked the game, overall - back in the day (96-97).

I never finished the game. I should've just played the main quest and waste less time exploring.

Don't forget the doors that would outright kill you, and the stairs that you could easily fall through, placing yourself out of bounds. (There's a reason why, in later Bethesda titles, if you fall too far, you're teleported to a specific spot in-bounds; this Daggerfall "void" is that reason.)

The Moathouse in Temple of Elemental Evil comes to mind. I don't think there is anything for a thief-type character to do - there isn't a single trap to disarm or a locked door or chest. On top of that, several of the combats are sprung on you as ambushes. It's really poorly-designed, especially as a first dungeon in a WRPG. The temple itself is a bit better, but not by much.

Any level where human effluent is implied to be the major inhabitant.

Since Rougelikes don't qualify, I'll give an Dishonourable Shame to the Dark Crypt in Tome 4. A set dungeon that most builds/classes will have no hard counter for that turns into an escort quest on the fourth floor.

The Spiral Pit/Crypt of Drath in Exile 1+2 and onward. So imagine a dungeon where undead are constantly spawning, your automap doesn't work, and you get denied your light sources. Also, many undead in these games are actually dangerous. [url=https://homepages.uni-regensburg.de/~mim09509/Avernum/AvernumEscPit/Towns/SpiralPit.html]It looks like this.[/url]

You have to reach the centre of an already long dungeon to only find out that in the first games, the place is mega cursed and there's nothing you can do about it. There is no teleport spell, my friend. So you're going to have to walk out manually. Thankfully, Jeff is a somewhat merciful if cranky soul, so there's only a few more encounters on the way out.

All of the latter half of Lands of Lore. Ruined the great first half of the game (that actually got me into the only "DRPG" [as you've been calling them] I've ever started to enjoy). The White Tower in particular comes to mind. Especially level 3 of it. Agreed. You forgot all the instadeath traps that are going to catch you even if you went in on rogue! Arcanum was another game that I liked for a while, then it became like a completely different game.

Planescape Torment (despite me loving Planescape for ttRPGs) similarly was just meh too, once you started to have to delve into dungeons.

Is this part any better in the remakes? (Avernum 1 + 2, and the remakes of *those* games.)

The yuan-ti temple on Icewind Dale II. That was some reaaaally crappy design...

Well, it depends on how you define better. But there's also a reason why I used encompassing wording. The short version: It's a damn slog every time.

The tunnels by the dwarf city in Dragon Age Origins (I'm trying really hard to remember the name of that dungeon). I remember it just going on and on for hours with seemingly endless waves of enemies and dull, repetitive scenery. Truly a slog.

Are we going to count an ARPG as a WRPG? If so, Diablo 2's swamp area. Technically act 3's "overworld", but it's essentially a dungeon. If that's too broad, let's say Act 3's sewers. Almost as bad in layout, but more clearly a dungeon.

It's not that it's hard or unfair... But the map layout in that part of the game is awful, with tons of backtracking, false starts, dead ends, and boring fights. Unless you have teleport.

You're right, the traps are also hugely annoying.
In Arcanum's defense I would however say that those clan mines are the lowest point of the game. There's another large dungeon later on which seems to be similarly annoying, but you can skip it if you have a character with enough skill in persuasion. The rest of the dungeons aren't good either, but at least they're usually shorter or optional. Ice temple was also pretty tedious imo, too large and boring.

Deep caverns. I didn't find it that bad, but it seems to be a widely disliked part of the game.

Baldur's Gate 2's Irenicus Dungeon during the Prologue is not 'bad' per se, but it's an unnecessary hindrance everytime you want to replay the game. It's the classic equivalent of modern unskippable tutorial area.

Oblivion and Skyrim might be inferior RPGs in every way compared to BG2, but I appreciate how brief the tutorial dungeons are, and you're given the chance to reroll your character right at the exit of the dungeon, so you can just create a save file right there to use whenever you want to replay the game with different races/classes.

Well, I don't know about frustrating or unfair but I found a lot of the dungeons in The Elder Scrolls IV: Oblivion to be dreadfully boring. Despite the fact that Oblivion is my favorite game in the TES series, and my favorite fantasy RPG of all time, Oblivion's dungeons are absolutely a weak point... which is unfortunate because I absolutely LOVE the aesthetics of the Ayleids. I want to love exploring Ayleid dungeons but yeah, the dungeons in that game are just so boring. To be fair, that's probably because they only had one person designing the dungeons in that game. Thankfully, Skyrim fixed that issue massively and ended up creating some of the most compelling dungeons in the entire franchise.