Broken is a term used to refer to any card giving the user of the card an excessive advantage or defines the competitive metagame in a negative or imbalanced manner.
Though many rules exist regulating the use of certain cards, the term is purely subjective. Many cards that are considered such are usually Forbidden in the Advanced Format, while others classified as "broken" in multiple copies are Limited or Semi-Limited. Some existing cards may become retroactively unbalanced following the release of newer cards, strategies and Deck types, meaning some cards considered "broken" may only be so due to a card combo that utilizes the card's effects to an exploitative degree.
One of the primary methods for gauging a card's balance is its consistency and cost required for use. Although some FTK and OTK combinations can be labelled "broken" for executing winning formulas that prevent opposing players from responding, they are often inconsistent and, therefore, balanced.
The term "broken" is also used as hyperbole by many players, to describe any card said players have difficulty dealing with. The term could be used also to refer to a combination of cards, ones that cause loops and quick destructive power within the first couple of turns in a duel, leaving one player unable to stop it. An example might be the now infamous "Wind-Up Loop", which on the first turn has the potential to rid a player of their entire hand, leaving them hoping for a top-decking solution.
- Mind Control - Your opponent can choose a face-down monster you control, flip it face up, and use it as a Synchro Material Monster or Xyz Material. (This card was created when there were no such summons, working as an example of a card getting broken due to a later released combo.)
- Black Luster Soldier - Envoy of the Beginning - A card most people can easily forget about, this card itself isn't as difficult as one might make it out to be. Most players wouldn't rely directly on this card, but rather would use it to further beef up a stacked field. An opponent can clear your field with a few cards, swarm their field with many monsters, and then summon this card to ensure an OTK. A player wouldn't even have to attack, just using its Banishing effect to get rid of any pesky monsters and allow for a swift beatdown.
Examples of Forbidden cards widely considered "broken":
- Chaos Emperor Dragon - Envoy of the End - An easily Topdeckable summoning (only requiring a LIGHT and DARK monster in the Graveyard) with high stats, and can wipe the entire field and hand at the same time while inflicting (usually) massive burn damage for only 1000 Life Points. This card, along with the following card, is widely considered to be the most broken card in the entire game due to their incredible synergy, and both are also among the many reasons why the Ban List exists in the first place.
- Yata-Garasu - Infamous for being one half of the Yata-Garasu Lockdown, which involves using Chaos Emperor Dragon's effect to clear an opponent's field and hand, summoning Yata-Garasu, and continuously attacking them. This leaves them stuck in an infinite loop where they are unable to draw cards, forcing them to forfeit the game and essentially resulting in an instant win.
- Raigeki and Harpie's Feather Duster - Able to clear opponent's field while leaving your field untouched without any form of cost.
- Imperial Order - Locks all Spell usage over an extended and player-controlled period. While its upkeep of 700 Life Points can be seen as proof that even cards featuring drawbacks or cost for use may be considered "broken", the cost is optional, meaning that the user can cut off an opponent's spells until their next turn with no cost. As such, "broken" cards are often designed with balance in mind, but due to players finding loopholes and exploits in their effects, they become broken as a result.