In Friend Like Me, Scar mentions dreaming about forcing Mufasa to eat Simba.
In Make or Break, Shenzi suggests slashing Nala's face to ruin her beauty.
In Magic Mystery Show, we get a good idea of Hago's cruelty when he kills his assistant Kitu by overloading his brain.
In Dead as a Dodo, Simba and Nala worry about being dragged into Hell by the Devil. Of course, the scene is played for laughs...
In King's Ransom, the text description of the Outlands makes it seem very nightmarish indeed...
Your Worst Nightmare is obviously a literal example, though Hago also gruesomely describes Simba's possible death, even adding he would like to drink the cub's blood afterwards.
In Miss the Girl, Hago claims he will kill Nala via a "brain overload."
In Zazu's in Charge, Hago speculates if the "Death Blaster" still works on his staff, and proceeds to test it by blowing up a large rock.
In You're Fired, the hyenas make several gruesome threats directed towards the cubs.
In Hago's Little Puppet, Hago hypnotizes Mufasa, turning him against the cubs.
In Army of Evil, Simba and Nala venture down into a dark cave, only to discover drawings done by Scar of them dying in various gruesome ways, including falling onto sharp rocks and being torn to shreds by hyenas.
Friends to the End has some rather nightmarish scenes concerning Scar. In particular, he rapes Uzuri, a teenage lioness, before sinking his claws into her stomach.
The quote below is another example:
Scar: I was actually thinking of subjecting Simba to some visual torture first. That young Nala cub is quite attractive, actually. I'm sure I could do something purely despicable to her that Simba could watch.
Series Two actually starts with a Nightmare Fuel moment, as Life Hurts opens with Hago's spirit torturing Simba in the first of many nightmares throughout the series.
The more menacing Mtumwa in Mtumwa Strikes Back would count on his own.
The Hago nightmare in Two Cubs and a Baby, as well as Simba and Nala's exaggerated fears of what the baby's mother would do to them if something happened.
In Tama's Bet, the idea of your boyfriend slowly becoming meaner and nastier would certainly count.
Simba and Nala briefly discuss their recurring nightmares.
The description of the Farlands would certainly indicate it to be full of this trope.
In Night Terrors,, Tama's transformation into a vampire would count. The text repeatedly describes how horrifying the vampires look with red eyes and long, pointed fangs.
In Sick Simba, the sheer concept of being slowly eaten away by an illness is quite terrifying.
The Royal Reaper is all about this trope, as it basically plays like a horror movie. Simba's story about the Reaper, while awesome, definitely qualifies, as he describes how the Reaper murders his victims in gory detail. The scenes featuring the Reaper would also qualify. His voice alone is scary as heck.
The flashbacks about Tojo's pride being burnt down by his father, the king, are quite frightening too.
In All Alone, Usaliti reveals he sent the Pridelanders to the Dark Place. At the end, Simba sends him there instead.
Who Are You opens with a brief Hago nightmare, but soon descends into hilarity and sweet moments.
In Goodbye, Nala, Simba reveals that he had a nightmare where his entire family, including Nala, killed him.
The scene with Nala and the hypnotized Sarafina.
Nala being drained of her energy by Tama.
In Hypnotic Glint, Simba tells Nala about a nightmare where all of his loved ones, including her, dissolved into bones and organs while trapped in a fire.
In The Royal Challenge, Tama is forced by Hila to infect Nala with the Unyevu disease, which will drain her of her energy within an hour unless she is rescued.
Nala being tortured in The Return of Hago.
Hago is killed when Nala throws his staff at him.
In The Prince and the Frog, Froggy sticks his tongue in Simba's ear in order to brainwash him.
The Mungu Pride's threats in God of All would count.
The scene where Duni becomes Shocker is extremely terrifying.
Shocker's very presence is quite nightmarish as well.
A lot of moments in Darkness Falls would most certainly count:
Death's initial appearances, where he's nothing more than a pair of glowing red eyes.
When it turns out that Death has possessed Haiba to gain access to the world of the living. Imagine how frightening that would be...
The moment when Death finally unveils himself to the cubs in all his nightmarish glory.
Death's murder of Nala and the Pride Landers.
Chaos attempting to crush Simba and Haiba.
Simba and Death both experiencing the pain of being completely destroyed.
Simba's parents are possessed by aliens throughout this series. Could also double as Paranoia Fuel.
In Drought, Simba wakes up underwater before being "rescued" by Maji.
The sight of her dried-up victims is a disturbing moment.
In Dig It, Maana is dragged into a dark pit by the vengeful skeletons of cubs at the camp. He certainly deserved it, though.
The titular character in The Interceptor is quite nightmarish in this initial appearance, as is the scene where Simba's "dark side" first intrudes on him. Not to mention Kazi's claim that it takes two or three days to die while being digested by The Interceptor...
The opening scene in Shocker's Revenge is quite nightmarish, as it depicts a lioness named Elsa running through a fierce thunderstorm before Shocker appears and kills her.
Quite a few moments from The Blood Line:
Cub Sarafina in the fog, listening as Vitani cackles, "She doesn't know! She doesn't know!" over and over again.
Muerto's death at Vitani's fangs.
Father's enigmatic nature, combined with the fact that he's six million years old, is disturbing enough.
Nala's first encounter with the Family of Blood.
Sarafina attempting to kill Nala as a vampire.
The Family of Blood melting away to bones and organs.
In Changes, the dark voice in Simba's head turns out to be Froggy, who had burrowed his way into the cub's head and manipulated his mind for quite some time.
Nala's glowing red eyes might count as well.
Two moments in Tama's Trouble:
Hago's murder of the Mungu Pride, complete with hanging their skulls from the trees.
Hago's death, as he burns into a skeleton. The scream at the end of this recording only adds to it.]]
The story Survival has more than it's fair share of nightmarish moments:
The story opens with Nala having been crushed by a boulder. The way the text describes her slowly dying, unable to make any noise, is simply terrifying.
Binamu is impaled when a strong wind blows a twig into her stomach.
Quite a few things from Rebirth:
The sheer concept of Scar, of all villains, being invincible.
Shocker's eyes being described as looking dead on the inside.
Shocker's story about the "Taka" name.
Scar's resurrection, followed by him walking out of the red mists, cackling evilly.
"My name is Scar. You will learn to fear it." Oh, we already do...
Scar attacking Haiba.
Haiba's condition at the bottom of the cliff.
Simba's horrified reaction upon Haiba mentioning Scar's name.
Scar's terrifying shouting as he enters the den, followed by him enslaving the pride.
Scar's death, as awesome as it is.
In Everyone Loves Nala, Shocker suggests poisoning the waterhole as a way to kill the cubs. Interceptor enthusiastically responds, "Ha-ha-ha! I like it! So we poison the little brats and watch as they vomit up their own guts!"
In Clone Wars, the scenes with Nala and her clone would count, as well as the idea of realizing you aren't real...
A few in The Beginning:
The concept of The Scavengers, attractive cannibal lionesses with red eyes and long sharp fangs.
The Scavengers eating the entire staff of Jowai Resort.
The Scavengers devouring each other.
A few in The Chase:
Aibu slashing Ndugu's throat.
The creatures are quite monstrous and intimidating, resembling bear-lion hybrids about 3 times the size of either species.
Aibu throwing Dada into the deep, black pit in the middle of the Dark Caves.
The creatures eating Aibu.
The sandstorm in The Curse of Death would qualify.
In One Bad Night, the story as a whole would count, since it involves The King of Dreams.
The creatures from The Chase returning.
Nala, Haiba and Sarafina attempting to kill Simba.
Nightmarish moments abound in Tojo's Tyranny:
The scene where Tojo is possessed by the staff.
Tojo attacking Tama and burning down the jungle.
Hago's cobra staff coming to life and killing Hago for good.
A couple things in The Evil Serpent:
Nyoka may be an awesome villain, but there's no denying he's just a tad creepy.
The discovery of Tojo's corpse: "A body was lying on the ground in front of them. Its eyes had been gouged out, just one of them hanging limply from a socket by a thin line of muscle and sinew. Chunks of flesh were missing from the gory corpse, most likely pecked away by hungry buzzards. The foul odour of blood and rotting flesh invaded their nostrils. It wasn't until they saw the blood-stained golden staff sticking out of its chest that they realized who it was."
Simba impaling Nyoka with a stick.
Several things in The Lost World:
The Hunters are rather cold and menacing villains. Particularly because they have hypnotized dinosaurs under their command.
The description of Maono's corpse. "The body...had been completely torn open from the chest. His lungs had been wrenched clean out, rotting remains strewn across the ground. His eyeballs were completely gouged out, leaving only black, lifeless sockets. All four of his legs had been ripped away; just four bloody stumps remained. The foul odour made them all want to be sick."
Simba killing Ubongo and Misuli, and leaving Muuzaji and Kununua to be devoured by the mother T. Rex.
Haiba slamming Tama's head repeatedly on a sharp rock, not listening to her screams.
In the follow-up story, Haiba's Wish, Wazimu changes Haiba's past, but it results in his own mother attempting to kill him for murdering her son...Simba.
In the story after that, Return to Camp Kazi, when the cubs look at the corpse of Kambi, they discover that the cub's eyes are completely blank.
Shauri revealing his true identity as The Thief would count too.