When you realize that those kids outside the cupcake hut are exactly what you dread they are... This is a game where being Genre Savvy can make things much easier — or much nastier.
The suspense of going through Dahlia's woods. Her "swooping down" music!
The wolf in KQ1 & 2.
The ogre. In the original, he just shakes you around. In the Sierra remake, you get into a Big Ball of Violence, with him holding your limp body. Neither of these are particularly terrifying. But in the AGDI remake, the ogre just grabs your head, literally crushes it, and blood trails out of his hands.
Raiding the Vampire's castle is nerve-wracking in the canonical game, but AGD cranked it up a few notches. Seeing what you were expecting to be the friendly monk from the canonical game transform into a werewolf? Oh, Crap!. Seeing Graham pinned to the wall, Caldaur's hand around his neck, the music shrieking in the background? Oh, CRAP! Being pinned down by the Brotherhood between the swamp and their jaws? OH, CRAP! And doesn't vampire lore show that a cross will repel it? Let's use it on Caldaur... nope, he (while still holding you by the throat) takes it, kisses it, and says "God Bless Kolyma". CRAP!!!
They also revamped the whole area making it creepier, complete with Dramatic Thunder and gothic music.
Navigating the Sharkees' land is an equally frustrating experience.
Notably in the Sharkee's Throne room, while distracting the humanoid shark guards, you have to sneak into the treasure room, but you have to do a (simple enough) password memory puzzle you saw the King use earlier. While doing the puzzle, you're on a timer; if you don't do it fast enough, the Sharkees will kill you. Though to be fair, you have the option to skip the puzzle, but you won't get the points.
The ferryman is especially creepy, with his low gravelly voice added to the fact his character portrait is a rather well detailed skull face with bright red glowing eyes.
The two ghosts guarding the castle. In the original, they were just floating white ghosts. In the remake, they have scary half-skeletal half-ghost-like appearances. Sweet dreams.
Half-expecting, half dreading you miscalculated by just that much and that Manannan would come back at any second and turn you to ash. The ominous organ music that plays when he appears doesn't help. Worse, this was a timed game, and you had a lot to do with very little time to do it. Miscalculate the margin of error, and poof!
Screwing up the spells. A typo could be lethal in this game. Sometimes led to Have a Nice Death — but not usually. Add it to the time limit of knowing Manny could come back at any second and strike you dead just added to the tension.
Adding to the Paranoia Fuel of Manannan's house, Manannan will kill you if he happens upon you while you're carrying an item that can be used for spellcasting... which includes something as mundane as a fly's wing. You have to hide such items away under your bed (your only safe space in the house) while he's around. Granted, the game helps you out a bit by showing a red outline around dangerous items in your inventory, but it's still a nasty way to keep you on your toes.
The Ogre. His wife is even scarier to some players. The way she drops her kill for the evening and goes after YOU...
The unsettled ghosts... especially the cradle that rocks, despite being completely empty, a baby's haunting cry splitting the air, and realizing that baby has probably been manifesting for many more nights than the poor dear ever saw alive.
Sneaking around the castle when even the slightest misstep means a nasty death at the bottom of the stairs, or capture.
Also, trying to picture Lolotte's dying screams. *shudder*
There's also that massive truck of Fridge Horror that hits you when you realize just how badly and on how many levels Lolotte had twisted up poor Edgar. She twisted his body into a hunchbacked form that was likely in pain all the time, tried to pass him off as her son when we later find out she'd kidnapped him, and was trying to twist his mind as well. *Wince*
How about if you eat the magical fruit and take the amulet back to Genesta, then get sent home to watch Graham die anyway?
How about Rosella having to go gravedigging, surrounded by a horde of zombies trying to grab her? If you do it correctly they can't harm her, but geez!
With the unsettled ghosts previously mentioned, you actually take turns dealing with both. Dig up a item while dealing with zombies, deal with a freaky ghost, go back to the zombies again, then another ghost. About 4-5 times in succession.
If players try to make Rosella enter the mansion at night without protection, a zombie leaps from the bushes by the front door and turns her into a zombie. It means a zombie was just waiting there to attack anyone who came by at night. If you have the amulet or it's daytime, it doesn't appear, but it's still there....waiting.
Yeah, the Forest Witch was a sadist psychopath. But did she really deserve an And I Must Scream defeat? Especially since she's trapped in there until someone frees her, and the most likely scenario is that the genie sent her to where the lamp originally was... in which the only item that can open said cave is destroyed forever.
Alexander being captured by the Druids and put up in a wicker cage to burn to death. There are times when being a mythology geek adds a few new ways to wince. This would be one of them. Burning to death is not a pleasant way to go, either.
Just about anything on the Land of the Dead. Creeping zombies of those whose torments drove them mad, and having to dodge them, lest a single touch cause Alexander's flesh to dissolve! There's the door death, the River Styx death, seeing the walls and twisted passages of the Land of the Dead, and realizing they are literally Samhain's flesh as he has fused with his hellish throne, and the land he rules is literally his body.
Sipping the "Drink Me" without knowing it only knocks you flat for a few minutes. The animation is unsettling to start with. The narrator and Benson's voice acting do not help.
Navigating the catacombs. So many ways to go wrong, so many death traps, and no warning. Traps everywhere, skeletons everywhere, and if you are traversing it for the first time, with no idea where the minotaur is? Heck, even if you know where you're going, confronting the Minotaur is pretty tense, especially when you look at the ritualistic altar on which he was planning to do Gods-knew-what to Celeste before devouring her!
We know from the first meeting Alhazred is no gentleman. When we find out what he did to Cassima's parents, he turns into "detestable slime bag." When we see that he was behind the islands' discord and colluded with Mordack, he jumps up to "pile of shit." When we realize that he plans to "dispose" of Cassimaafter the wedding night, Alhazred turns into "Alex, skewer the bastard NOW!"
Alexander interrupting the forced wedding of his beloved Cassima to Alhazred... only for Cassima to affirm that she is in love with her bridegroom, and order Alexander's death. Of course, it turns out that she's actually the genie in disguise, but it's still a nasty shock.
The Boogeyman — a bony, ash-faced creature with a huge gash of a mouth, rows of enormous teeth, empty black eyes, and a bone-chilling voice — roams the land of Ooga Booga. If you stand still for too long, he'll dig his way out of the ground and jump on you, apparently eating you offscreen. And how does the game tell you he's about to make an appearance? When you hear this.
The ghostly wanderer who shows up in the desert, while not evil, is pretty creepy. He gets even creepier if you give him the salt water; while he doesn't hurt you or make the game unwinnable (all he does is give you a What the Hell, Hero?), the fact you clearly see him in pain while his eyes glow yellow for a second... This scene was rather disturbing.
There's also the giant scorpion in the desert temple.
The cursed crying woman; when Rosella asks what's wrong, she says it's her face. She then shows her face (facing away from the player) to Rosella, who screams, and immediate game over. How can a face be so scary that you can die from fear just by looking at it?
Further Fridge Horror, read the KQIV entries above. After all of those, THIS is what ended up killing her from fright? (Keep in mind KQIV rivals VI for the title of scariest King's Quest game.) It seems this may be a contender for the most literal "Nothing Is Scarier" in the entire series.
Rosella and the Troll King being trapped in the coffin is already pretty scary, but then the skeletons start trying to dig their way in. If you take too long finding a way out, a grinning skull will poke through the wall expectantly. Cue Game Over.