Several of the Shadow Games are incredibly dangerous, even if the results are toned down to be illusions rather than fatal.
While awesome, Yami Yugi's powers in this series include reality warping and conjuring up whatever's needed for his shadow games, like transporting Ushio to another dimension filled with a giant tower and playing cards that stick on the wall.
Ushio's Penalty Game was changed from him seeing everything as money to being eaten by monsters. It's still just an illusion that he likely gets over, but one is considerably less pleasant than the other.
Episode 4 has perhaps the most horrific scene in the entire franchise. Yugi battles a thug obsessed with watches who stole Honda's. The Shadow Game has them trying to recover it from a periodic spring, before a giant pendulum takes their hand. When the thug tries to cheat, the pendulum automatically swipes across his hand—and instead of blood, he sees gears and sprockets in the gash, his watches are bonded to his skin, and he lets out a horrible scream as his glasses fall off and reveal clock hands in his eyes.
Shadi's Shadow Games are about as bad as in the manga, and being animated ups the surrealness and adds claustrophobic close-ups.
Episode 7, the anime version of the digital pets chapter from the manga. Kujirada appears to be the bad guy, like in the manga, until the real Big Bad of that episode reveals himself in the form of a creepy, glasses-wearing little kid known as Haiyama, who until then was considered the victim of Kujirada's bullying. Turns out Kujirada is the victim and Haiyama's the one who bullied him senseless with a whip, and it's implied he has a long history of doing this to big, tough-looking guys to make them do his bidding. His Penalty Game is an illusion of being eaten by his digital pet, which he mistreated. It's one of the few instances in which the anime was darker than the manga.
Count Ridley Sheldon collects creepy dolls as a hobby, using a life-size puppet of the school nurse to duel Yugi before dueling Yami Yugi in person in a mansion filled with dead-eyed, staring dolls. Yugi himself comments on how creepy it is.
Episode 11 involves Warashibe Kiyami, a Psychopathic Man Child college student with a very obsessive crush on Miho who calls her his Capumon goddess. At first he gives her gifts, then recruits Yugi into 'rescuing' her, but when she rejects him he poisons Yugi's friends with polluted water and plans to keep Miho in a giant capsule as a trophy. What's worse is that Yugi and his friends don't realize how unhinged he is, with Anzu blaming Miho's pen pal letter for the mess.
Ryuichi Fuwa has an Ax-Crazy moment in episode 12. While trying to draw out Dark Yugi, he wonders whether Yugi's 'other face' is literal and says he'll grind off his skin if need be.
Episode 13 involves the fake psychic Kokurano, who will do anything to prove that he's a real psychic. He goes as as far as to set his classmate's house on fire, tried to harm Jonouchi and Yugi with a falling light, tried to crush Yugi beneath multiple bookcases, and chloroforms Anzu with the intent of doing some sexual things to her while she is unconscious.
Episode 15 had Risa Kageyama and her two identical sisters, witches who want to collect Yugi's Violet Hecate card and stole the Millennium Puzzle to do it. They were about to defeat Yugi in a duel until Kaiba stepped in, they almost beat Kaiba as well, and get no punishment for their actions. Even worse is that they can easily act like kind, sweet girls, with Risa befriending Yugi at first. They also wield whips, and the scene where they break into Yugi's house has them dropping in from above and attacking Honda and Jonouchi as they chase Yugi down.
Episode 16 has a corrupt doctor blackmailing Jonouchi by threatening to remove Shizuka from the hospital. The situation is so awful that Jonouchi cries over it, and when Yami Yugi dispenses justice, the doctor's penalty game is to see zombified wraiths of patients that died due to his negligence.
Aileen Rao has hypnotic powers and hypnotizes Anzu into being frozen like a statue, then endangers her life with her pet tiger. She relates this to Yugi while calmly drinking tea, and uses her words and the threat to Anzu's life to psych him out and nearly win. Death-T reveals she's good at physical fights, too.
Unlike the manga, Imori is corrupted by the dragon cards' powers and his evil soul is stolen at the end. It doesn't make what happens to Yugi any less terrifying, and unlike the manga, the Dragon Block game has an effect on a place in real life, creating impossible chasms of water in the sea.
Episode 19 involves Kaoruko Himekoji, a model who humiliates Miho at a beauty contest by drugging her and ripping her dress apart. Dark Yugi challenges her to a game where they would pick roses from a collection, the loser being the one who picks the last rose. After he wins by picking the second-last rose from Kaoruko's hair, Yugi gives her a Penalty Game where she sees herself as old and ugly... and with snakes wrapping around her wrists.
This version of Seto Kaiba is even worse than his manga counterpart. Kaiba and Yugi’s first duel is changed into a draw, so neither side wins and he doesn't get a penalty game. Kaiba becomes so furious at the duel ending in a draw that he sends his Game Masters to kill/defeat Yugi and his friends, stalks Yugi to see if anyone else is trying to beat him in a duel first, and builds Death-T for the purpose of killing Yugi and his friends. Making it worse is that in this continuity, since he hadn't lost to Yugi yet and hadn't received the Experience of Death, he came up with the punishment on his own rather than recreating what he'd gone through.
In episode 20, Kaiba's butler, Daimon, is physically weak and lives in a life support capsule that he can only exit for a short amount of time. Kaiba wakes Daimon up, tells him to go fight Yugi (with Anzu as bait), tries to get him to cheat at Duel Monsters, and when he loses, Kaiba leaves him for dead right after Daimon expresses hope that his kindness can be restored. Worse is that while the flashbacks show Kaiba as a young child having fun, nothing of what Gozaburo put him through from the manga is shown. While Daimon's tutelage in games could be taken as Kaiba going to the logical extreme, it implies that Kaiba changed on his own rather than from suffering abuse.
During Death-T, Ryou Bakura is among the crowd, but he leaves when the Ring causes him pain and starts to glow. When Jonouchi and Miho look for Honda, who Yugi believed wasn't dead, they run into Bakura, who wordlessly points out that Honda and Yugi's grandpa have been trapped in an hourglass that's filling with water. And then he disappears. To save them Jonouchi and Miho had to play a real-life fighting game against Aileen and Ryuichi under penalty of their deaths.
