The original Yu-Gi-Oh! anime followed the adventures of Yugi and his friends as they traveled the world and engaged in numerous duels. Throughout the series, viewers were introduced to hundreds of different Duel Monsters cards, including some overpowered Yu-Gi-Oh! cards like the Dark Magician and the Blue Eyes White Dragon.
The most powerful Yu-Gi-Oh! cards would probably ruin any reasonable trading card game. Anime about trading cards, however, operates on a different set of rules. These cards possess arbitrarily high Attack Points, insane special abilities, and can unfairly cripple an opponent. These cards sometimes required complex strategies, but often were just unfairly overpowered in order to save the protagonists. These Yu-Gi-Oh! cards are too powerful, and often didn't make any sense within the rules of the actual game.
Simply put, there is a reason why the real world versions of these cards have been altered to drastically reduce their power.
This terrifying God Card is without a doubt a force to be reckoned with. Just at his base, Obelisk the Tormentor possesses 4000 Attack and Defense Points. As if his extremely high Attack and Defense weren’t enough, Obelisk the Tormentor also has two devastating special abilities. The first allows Obelisk to destroy all Monsters on the opponent’s side of the field and inflict 4000 points of damage to an opponent’s Life Points, all for the low cost of sacrificing two Monsters.
What really makes Obelisk the Tormentor overpowered, however, is its other special ability. By sacrificing two Monsters, the user can make Obelisk the Tormentor’s Attack power infinite. This means that no matter how many Attack Points an opponent's Monster possesses, if Obelisk strikes it in Attack Mode or attacks an opponent’s Life Points directly, the duel is immediately over. With his raw destructive power and insane special abilities, Obelisk is truly worthy of the title Tormentor.
The Crush Card is utilized by infecting a Monster with less than 1000 Attack Points. When that Monster is destroyed in battle, the Crush Card infects the opponent’s deck and prevents them from using any Monster with more than 1500 Attack Points.
This card is to high-level Monsters what the plague was to 13th-century Europeans. There is nothing the duelist it’s used against can do to remove the damage done by this card: it’s active until the end of the duel. Preventing a duelist from utilizing their strongest monsters, without any type of penalty to the user, essentially ensures the opponent's defeat.
It’s not surprising that the Egyptian God Card touted as the greatest would also be overpowered. The Winged Dragon of Ra’s Attack and Defense stats are dependent on the Attack and Defense points of the three Monsters used to Summon it. This means that its Attack can easily soar well above 3000, unless extremely weak Monsters are used as tribute. Even if weak Monsters are used to summon Ra, its special abilities would more than make up for a lack of Attack and Defense points. The Winged Dragon of Ra has a special ability that allows it to absorb the Attack and Defense points of tributed Monsters, and then attack each Monster an opponent has on their side of the field.
Ra’s second ability known as its "God Phoenix effect," and it prevents the user from taking any damage. By paying 1000 Life Points while Ra is in this form, it can destroy all Monsters an opponent controls.
Its last, and possibly most devastating, ability is its “one turn kill” effect. This ability allows Ra to absorb all but one of its owner’s Life Points to increase its Attack and Defense Points. This means that Ra could potentially add 3999 Attack and Defense Points to its already existing stats. The Winged Dragon of Ra was an overpowered beast that even Yugi barely managed to defeat, even when he was using the combined power of Slifer the Sky Dragon and Obelisk the Tormentor.
The Golden Castle of Stromberg is a card with an interesting backstory. It was originally crafted by Duel Monsters Creator Maxamillion Pegasus, as he created a small number of cards meant to be used as prototypes while constructing the game. It was eventually utilized as a prize during a tournament, but was never meant to be used in actual duels. In fact, it was only able to be played when an antagonist uploaded a virus, allowing it to be used against Yugi during a duel.
So what can this unique card do? First, the user cannot Normal Summon, but can Summon a random Level 4 Monster or lower their deck (and said Monster must attack each turn). It works out, since their opponent’s Life Points will be wide open. See, enemy Monsters must attack each turn, and upon attacking are immediately destroyed. For added fun, they inflict half of their damage to the opponent’s Life Points.
The Golden Castle of Stromberg remains active throughout the entire duel, as it cannot be destroyed by Spells, Traps, or Monster Effects. The only drawback is that it costs half the user's deck to use, but even that can be turned into an advantage. A duelist can fill their deck with Traps, Spells, and Monsters with effects that activate once in the graveyard. It’s unknown why Pegasus would create such a card, since it was only developed as a prototype. He made a wise decision to keep it out of the game, and not subject duelists to this immensely overpowered Field Spell.