Determining the most powerful Yu-Gi-Oh card is subjective and can depend on various factors such as the players strategy, the format of the game, and the cards effects. However, here are some of the strongest Yu-Gi-Oh cards based on different sources:

• Meteor B. Dragon: This card has 3500 ATK and 2000 DEF, making it a heavy-hitting Normal Monster that can best most.

• Exodia, the Forbidden One: This card is considered one of the most powerful cards in Yu-Gi-Oh! and is still technically as dangerous now as it was back then. It was one of the first monsters introduced and is still a fan favorite.

• Number 16: Shock Master: This card has a lingering effect that completely shuts down your opponents ability to use any one of Yu-Gi-Ohs 3 major card types. Its not a hard once per turn either, so if your opponent summons 3, its over.

• Maxx "C": This card wins you the game against most decks when it successfully resolves.

• Holactie the Creator of Light: This card is considered the strongest card in the Yu-Gi-Oh! lore. It has infinite ATK and DEF, and its effect allows the player to win the game instantly.

• Boss Monster card: This card is not officially implemented in the Yu-Gi-Oh! TCG, but it has one of the strongest attack power amounts in the whole game. Its semi-official, is a severely rare card, and would decimate any player in one move.

Its important to note that some of these cards may be banned or restricted in certain formats of the game. Additionally, there are many other powerful cards in Yu-Gi-Oh! that can be used effectively depending on the players strategy.