Broken is a subjective term used to refer to any card or strategy that gives its user an excessive advantage, or a card or strategy that defines the competitive metagame in a negative or imbalanced manner. Most cards that are considered or found broken are usually Forbidden or Limited shortly afterward, though not necessarily always.
In general, the two primary factors for gauging a card or strategy's balance is its cost and its consistency. For example, some FTK and OTK setups can enable their user to instantly win the Duel without their opponent being able to respond when performed correctly; however, they are very often inconsistent (and leave their user in a highly losing position if failed), making them not broken. (On the other hand, FTK/OTK setups that are discovered to be highly consistent will be deemed broken, and generally their key card(s) made Forbidden or Limited.)
It is sometimes the case that existing cards or strategies become retroactively unbalanced due to the release of newer cards or mechanics. Other times, cards or strategies may become broken due to an unexpected and/or unintended interaction with other cards, strategies, or mechanics. An alternate definition of "broken" can refer to cards/strategies that become heavily used outside of their intended design due to an exploitation or loophole in said design, thus "breaking" the design.
Examples of non-Forbidden cards considered broken
- "Mind Control" - When released, was considered a bad/situational card and was Unlimited due to a "stolen" opponent's monster being able to do little else other than use its effects. With the advent of Synchro Summoning years later, a mechanic that the card did not prevent (a "loophole"), the usability of the card increased drastically, making it immediately Limited due to its newfound power.
- "Self-Destruct Button" - When released, was considered only useful in an emergency to get out of a hopelessly losing situation with a result not as bad as a loss. However, its effect became abusable in timed tournament Duels, as a player could use this card to legally stall Matches until time ran out, thus completely undermining the intended best-of-3 mechanic and potentially abusing the "sudden death" mechanic to an undesirable degree. This card is Forbidden in the TCG but Unlimited in the OCG. (For more information, see the Victory condition page on tournament time limit mechanics and the "Self-Destruct Button" Card Tips page.)
Examples of Forbidden cards considered broken
- "Wind-Up" Loop - A possibly unexpected lengthy combo involving using multiple copies of "Wind-Up Carrier Zenmaity" to repeatedly bring back and reuse the effect of "Wind-Up Hunter", which could wipe out an opponent's entire starting hand on the first turn, giving the user an overwhelming starting advantage with little to no chance for the opponent to respond. Soon after its discovery, "Wind-Up Carrier Zenmaity" was Limited and then Forbidden in the TCG; in the OCG, "Wind-Up Hunter" was moved directly from Unlimited to Forbidden instead.
- "Pot of Greed" - Released when the game was very new and it was likely difficult to anticipate the importance of card advantage in the future competitive metagame. Effectively gives the user an immediate unconditional costless +1 in card advantage, and makes it objectively superior to every other topdeck in the game, thus giving Deck constructors zero reason to not run the maximum number of copies possible in their Deck. Was made Limited and then Forbidden due to needlessly reducing Deck diversity and giving an arbitrary advantage to whoever drew it first.
- "Imperial Order" - Considered broken by both possible definitions due to its intended upkeep cost being exploitable to actually make the card much more powerful than it would be without it. As the cost is optional and kicks in only at the beginning of the player's turn, and as the card is a Trap Card that can be activated during either player's turn, and as Spell Cards are almost always used during one's own turn and rarely during the opponent's turn, a user of this card can activate it during the opponent's turn (even in immediate response to a Spell they just played), then intentionally not pay the cost and allow the card to self-destruct during their own turn, thus locking the opponent out of all Spells for a turn while not affecting their own Spells at all, with all this at zero cost.
- "Victory Dragon" - Likely not intended by design, the ability for the card to interfere with something outside of the current Duel (namely, the result of a future Duel) made intentionally surrendering (or even intentionally breaking the rules to get a Game Loss penalty, in the event surrendering is not allowed) an actual viable strategy, anecdotally leading to a number of undesirable ruling disputes and arguments over "unsportsmanlike behavior" at tournaments. The card was later moved directly from Unlimited to Forbidden. (For more information, see the "Victory Dragon" Card Tips page.
- "Mass Driver" - Likely intended only as a last ditch method to inflict chip damage on the opponent by giving up large amounts of field advantage, its effect and the ability to activate it an unlimited number of times per turn led to the creation of a nearly unstoppable FTK strategy years later, with the advent of strategies that could use loops to Summon an unlimited number of weak monsters to the field (which would otherwise be not nearly as useful, with the natural 5-Monster Card Zone limit). Was soon moved directly from Unlimited to Forbidden.