Ripping people's hearts out, enslaving children, crocodiles and chilled monkey brains feature, although the most terrifying thing of all is that they brainwashed Indiana freakin' Jones. It's not easy to see your hero attempt to kill his love interest. It takes heavy pain to snap him out of it, luckily.
The way they brainwash Indy is pretty unsettling: they force him to drink a chalice topped with a rotting human skull which is filled with blood that would put the victim into a "black sleep". When they finally manage to make him drink the blood, we later see Indy writhing and screaming. The ambiance is very dreamlike and when he finally succumbs, he starts to laugh.
When Short Round and Indy are exploring the secret passageway in the palace, Short Round tries to open a door which collapses revealing two rotting corpses.
The Brainwashed Maharaja torturing Indy with the use of a Voodoo Doll, during the first time when we see him using it, he places it near a fire and Indy starts screaming in agony. What's even more disturbing is the Maharaja's Slasher Smile when torturing him
The spike room trap, which could only be deactivated by a lever that was covered with bugs.
When Mola Ram pulls out the sacrifice victim's heart, it is more terrifying when we find the heart is still beating. The poor sacrifice victim's screaming as his body is consumed by fire crosscut with Mola Ram laughing maniacally holding the guy's heart as it bursts into flames at the same time. Then we see his torched body dissipate in the lava.
When one of the slave drivers Indy is fighting gets his sash caught in a rock crusher and then gets dragged, feet-first, into it slowly screaming in panic and begging Indy to help him by calling out "Sahib!" over and over. Indy even tries to save the guy, but to no avail. Then the film cuts to above the crusher and we see a smear of blood on it. At this point, no one could blame Willie for looking away.
The Mooks who fell down into the canyon at the end of the movie, only to be devoured by crocodiles. Even worse, Mola Ram pushed several of them off the bridge to this fate.
Right after Indiana got the Shankara stones from the giant skull, he hears the sound of whipping and children screaming in pain. And each screams seems to get distorted into a monstrous roar. After the second scream, he looks at what appears to be human skin tied up above the wall. Then after the third scream (which is much deeper), he looks at the giant statue of Kali, which looks like it is staring at Indy.
A villain like Mola Ram should come off as almost Narmy, but the way he acts and fits right into the nightmarish setting of the Thugee temple just makes him terrifying. Ram isnt a twisted bastard hiding beneath a veil of civility like the main villains of the first and third films, he is an out and out monster.
Mola Ram: Drop them [the Shankara stones], Dr. Jones! They will be found! YOU WON'T!Hahahahaaa!GE-NA!!!note Get him!
The Thuggee assassin hiding among the murals in Indiana's room, who then steps out of the shadows and starts to choke him. Though it might be Nightmare Retardant when you realize he's hiding while Indy complains about Willie.
Indiana translates what the village leader said about what happened after the Shankara Stone was stolen from the village:
"He said when the stone was taken, the wells dried up and the river turns to sand. The crops were swallowed by the earth. The animals lay down and turned to dust. Then one night there was a fire in the fields. The men went out to put out the fire. When they came back, the women were crying in the dark... Children. He said they stole their children."
The bit where Willie is almost sacrificed is pretty terrifying, from when she tearfully begs Indy to help her, not understanding why he won't, to her hysterically and repeatedly screaming "No!" as she's lowered into the pit, to sobbing as she resigns herself to her fate. The quick shots of the worshippers chanting and cheering all this on doesn't help.