Yami Yugi 

An idiotic 5,000 year old spirit with a weird obsession with children's card games and "mind crushing" people. He has absolutely no memory of who he is and somehow wins nearly every game (Which wouldn't be so bad if there was an explanation of why he wins other then "He's the main character's (Yuugi) alter ego.) He also never shuts ups the "heart" of the cards.

- That is the American version
Manga Version:
A "psychopathic' 3,000 year old spirit with a weird obsession with all games. In the first seven volumes (The Shadow Games) he forces his host into a state of unconsiousness. During this time he challenges criminals to children's games and wins. (Unlike the American version there is a "reason" why the pyschopathic version of Yami Yuugi wins all the games. He never really actually wins if you think obout. His opponents' "sins" make the opponent lose.) After winning he plays a "penalty game" with the loser, inflicting pyschological toture on the loser. Often this toture is so great the victim end up feeling physical pain and in some cases commits suicide. In the later volumes (Duelist) Yami Yugi (realizes he has no idea who he is and decides to have the rest of the gang, which in the manga aren't complete idiots and have interests other then card games and "friendship", help him. However, unlike the Amercian version of Yami Yuugi, the manga version plays other games besides card games and seems to enjoy toturing people.

Me after watching the American Version of Yu-Gi-Oh!: Yami Yugi is probably the stupidest character ever! Honestly, he's the main character's alter ego! You'd think the creator of this show would give the main character's alter ego a more interesting personality and interests other then card games and "mind crushing" people.

Me after reading "The Shadow Games" and volumes 1 through 15 of "Duelist": ... I'm unsure which is more disturbing, the fact that Yami Yuugi challenges criminals to children's games, the fact that he inflicts pyschological totoure on them after winning, or the fact that he seems to enjoy it. No that not it. The most disturbing thing is that he takes over the main character's body just to do these things. Wow, I'm surprised nobody bothered to send the main character to a pyschiatrist or a priest yet.

Once again 4Kids demonstrated their power to turn a "pyshco" into a complete idiot.

Yami Yugi by pyschotoidiot December 12, 2011

Yami no Yugi 

Yugi Muto's dark half in the anime Yu-Gi-Oh!. He is the spirit of and unknown Ancient Egyptian Pharaoh who is anywhere from 3,000 to 5,000 years old.

4Kids made him into a prick that never shut's up about justice and a Literal "heart of the cards." In the 4Kids version of the anime, Yami no Yugi spends most of the duels Talking!
In the Japanese version of the anime Yami no Yugi still doesn't seem to know when to shut up. However unlike in the 4kids version, Yami no Yugi doesn't shut up because he's busy taunting his opponent while planning his next move, and Not mindlessly going on about justice and what-not. He also does mention "heart of the cards" a lot, but it's a metaphor. (Trust in yourself and in your abilities etc.)
Now if you read the manga or watch Season 0. that is where Yami no Yugi gets a little scary. Here you don't see the 4Kids prick, or the Japanese anime Yami no Yugi. Instead you get a slightly sadistic spirit that likes to play penalty games on his victim, where said victim usually ends up suffering severe torture of some kind, and in the worst cases death. In the manga and Season 0, Yami no Yugi forces Yugi into unconsciousness so the spirit can do as it pleases.

4Kids Yami no Yugi: The cards have a heart!
Random Person: They're freaking pieces of cardboard you prick!

(I'm just making up the cards. I don't remember if they exist or not)
Regular Japanese Yami no Yugi (talking to opponent): You're a coward you know that? I bet you would never dare play if you couldn't rely on that Dark summon card of yours. (Thinking: I should use Revealing Sword and then use an anti-defense card.)
Random Person: Yami no Yugi actually has a brain!

Manga/Season 0 Yami no Yugi: Penalty game! *Laughs as unfortunate victim suffers severe torture.*
Random Person: I don't know what's scariest, Yami no Yugi, the fact that Yugi is completely oblivious to Yami no Yugi's existence, or that nobody has noticed anything strange about Yugi and sent him to a shrink.

Yami no Yugi by Anti-4Kids November 2, 2011