Don't let Yugi Muto's innocent demeanor fool you. He may seem like an innocent little sweetheart at first glance, but inside that tiny spikey-headed body lies a cold-hearted duelist. Well, inside the Millenial Puzzle, to be exact.

RELATED: Yu-Gi-Oh: Every Millennium Item, Ranked (In Terms Of Power)

Through the body of Yugi Muto, the spirit of Yami Yugi emerges whenever challenged to a make-or-break game of Duels Monsters. Yugi's victories may save the day in the end, but the King of Games is a crueler ruler than the public realizes. Here are some of the worst things Yugi Muto has done in Yu-Gi-Oh!: Duel Monsters.

10 Being A Complete Psycho In Season 0

Before the anime equivalent of Magic the Gathering was introduced in the series, Yu-Gi-Oh! was about a variety of deadly games performed by a sinister Yami Yugi. While the spirit of the Millenial Puzzle always had an edge to him, the Yugi seen in the earliest chapters of the manga was a complete psycho.

Many of the "Punishment Games" Yugi inflicted on the villains resulted in insanity or death. The most famous example of this is Yugi tricking a bank robber into setting himself on fire. While the first Yu-Gi-Oh! anime series (dubbed season 0 by the fandom) tone down these fatalities as mere illusions, the King of Games still came off as a deranged lunatic. It's no wonder why the second Yu-Gi-Oh! anime series decided to skip these controversial chapters.

9 Activating The Seal Of Orichalcos

It's not like Yugi to be backed into a corner, but his first matchup with Raphael during the "Waking the Dragons" story arc proved more challenging than he imagined. Raphael kept taunting Yugi into using the forbidden Seal of Orichalcos: a card that steals the loser's soul for The Great Leviathan.

Raphael got his wish, as Yugi activated the Seal of Orichalcos to give his monsters the much-needed power boost. Yugi was soon corrupted by the Seal of Orichalcos, as he callously sacrificed his treasured monsters for any cheap blow he could get at Raphael. And because of the dark powers of the Seal of Orichalcos, the monsters used in the duel were sentient during their destruction. Yugi even sacrificed the Dark Magician Girl! Yugi's disrespect for his cards came back to bite him in the end; costing him the duel and little Yugi's soul.

8 Going Berserk On Weevil

Speaking of "Waking the Dragons," easily the most messed up moment from that saga was Yugi pummeling a child to near-death via a children's card game. In his defense, that child was Weevil Underwood. Ever since he threw away Yugi's Exodia cards, Weevil has been an annoying pain in the butt. Weevil crossed the line, however, when he tricked Yugi into thinking he tore up the card that contained little Yugi's soul, during their duel on top of a speeding train.

Enraged, Yugi defeated Weevil through the use of his Berserker Soul card, which allowed him to attack Weevil as long as he kept drawing monster cards. After Weevil lost the duel and was about to lose his soul to the Seal of Orichalcos, Yugi kept drawing monster cards to continue his assault. If not for Téa Gardner holding him back, Yugi would have kept attacking Weevil's soulless body.

RELATED: Yu-Gi-Oh! Ranking All Of Yugi's Friends From Worst To Best

7 Cheating At Duels Monsters

King of Games? More like King of Cheaters. Ever since the beginning of the Duelist Kingdom arc, Yugi Muto has cheated his way to victory. Attacking the Full Moon during his battle with Mako Tsunami? Destroying the "floatation ring" of PaniK's Castle of Dark Illusions? Fusing Mammoth Graveyard with the Living Arrow card?

All illegal moves in the Duel Monsters' rulebook. Even in the Battle City arc, where the anime was following the real-life card game more closely, Yugi was still bending the rules to his favor. Who says you need money to screw the rules?

6 Endangering His Grandpa

Yugi Muto is a terrible grandson. He's constantly putting his poor grandpa in danger. The old man nearly suffers a heart attack after dueling Kaiba in episode one of the anime and loses his Blue-Eyes White Dragon card too.

His soul got sucked up for an entire season by the Millenial Eye of Maximillion Pegasus. It was later knocked out by Bakura during the Battle City Tournament saga. And was briefly killed in Yu-Gi-Oh! 3D Bonds Beyond Time. An old man like Solomon Muto shouldn't have to suffer like this.

RELATED: Yu-Gi-Oh!: 10 Relationships That Changed The Series Forever

5 Toying With Shadi

On top of being a terrible grandson, Yugi's a terrible host to his mind guests. Near the end of the Duelist Kingdom arc, little Yugi is visited by Shadi and his Millenial Key. As the keeper of the Millenial Items, Shadi detected the sudden removal of Pegasus's Millenial Eye and suspected Yugi of the crime (when it actuality, Bakura was the culprit). Without giving Yugi a minute to react, Shadi invaded Yugi's mind through the powers of his Millenial Key to discover the truth.

Inside, Shadi discovered the split personalities of Yugi Muto: The innocent Yugi and the Mysterious Yugi. Yami Yugi confronted Shadi about his investigation, then allowed him free passage to his mind palace. Shadi was soon lost in Yugi's brain labyrinth and nearly fell o his death, if not for the help of little Yugi. If little Yugi wasn't there to guide Shadi to safety, Yami Yugi would have let Shadi die.

4 Letting Arkana Get The Buzzsaw

Aftermath of Arkana vs. Yugi in Battle City Yugioh

Let's get one thing straight: Arkana was not a cool dude. The shamed magician had no right to lure Yugi into a duel to the death during the Battle City arc, where the loser would have their legs chopped off by a buzzsaw (or, have their mind sent to the Shadow Realm in the 4Kids dub). With that said, not even a manipulated lunatic like Arkana deserved to lose his life in a Saw-like death trap.

After Yugi defeated Arkana in Duel Monsters, the buzzsaw began to rev up for Arkana, while Yugi was presented with the key to unlocking his shackles. While Arkana hid a second key under his sleeve, the mind-controlling Marik tricked Arkana into letting the key go, as he believed Arkana should pay for losing the duel with his life. During the aftermath of the match, Yami Yugi is seen being contempt with Arkana meeting his end through his own death trap. If not for little Yugi tagging in and saving Arkana with his key, the duel arena would have been a bloodbath.

RELATED: Yu-Gi-Oh!: Seto Kaiba's 10 Most Badass Moments, Ranked

3 Nearly Killing Kaiba Over A Card Game

Despite Seto Kaiba having the upper-hand during his rematch with Yugi at the Duelist Kingdom tournament, Yugi turned things around by fusing his Living Arrow card with Mammoth Graveyard (a cheating move) to infect Kaiba's Blue-Eyes Ultimate Dragon. Not only was Kaiba's most powerful monster being weakened by every turn, but he also couldn't attack Yugi's life points because of the never-ending spawning of Kuribos.

Losing this duel meant Kaiba's little brother, Mokuba, would never get his soul back from Pegasus. Because of the high stakes, Kaiba challenged Yugi to an ultimatum: Surrender the duel or he'll "fall" off Pegasus' castle. Yugi initiated the final blow. Kaiba was only spared because Tea cried out for Yugi, which caused little Yugi to regain control and surrender.

2 Torturing Kaiba

While his rematch with Kaiba is the closest Yugi has ever gotten to killing him, he's done so much worse to Kaiba in the manga. Their first encounter in the manga is similar to the Duel Monsters anime. Kaiba steals a Blue-Eyes White Dragon card from Yugi's grandpa, then challenges Yugi to a duel.

What's different is that after Yugi defeats Kaiba in the duel, he transforms Kaiba's soul into a Duel Monsters card and makes him experience countless deaths at the hands of other Duel Monsters. In a manga-only story arc, Kaiba traps Yugi and his friends in a deadly amusement park called Death-T. After defeating Kaiba again, Yugi sends Kaiba into a six-month coma by shattering his mind.

1 Forcing Yami To Go Out With Tea

Out of all the horrible things Yugi Muto has done, forcing Yami Yugi to go on a date with Tea is number one. Yami has never expressed interest in Tea. In fact, Yami actually encouraged little Yugi to ask Tea out.

But little Yugi surprised Yami (and Tea) with a last-minute date, and Yami couldn't back out because that would be rude. It was an awkward situation for everyone. Shame on you, Yugi. Shame.

NEXT: Yu-Gi-Oh: 10 Best Villains In the Series, Ranked