List of all the Battle city duels where one or both cheated, were seen by the Kaibas or other people but didn’t do anything to disqualify the duel:
1) the very 1° official duel (as said by Seto), Yami Yugi vs a rare hunter/Seeker, YY won but Seeker still used fake cards
2) 2° duel, Joey/Jounouchi vs “Esper”/Espa Roba, Joey won but Roba was helped by... his clones to see Joey’s hand
3) 5° duel, Yami Yugi vs Arkana/Pandora, YY won but Arkana used modified (aka illegal) Dark Magicians, there are also some death treats in this, in all fairness the Kaibas couldn't stop him because he also used an hidden, non-approved location (3 in 1 gg Arkana)
Note!) 6° duel, Joey vs Weevil/Haga, DOES NOT involve cheating, as strange it is, putting cards in your opponent's deck is a 100% legitimate move when the card is Parasite Paracise ¯\_(ツ)_/¯
4) 10° duel, Seto and YY vs Lumis and Umbra/Mask of Light and Darkness, Seto and YY won but Lumis and Umbra made the duel a death trap and used receivers to comunicate with eachother, which is against the rules i guess?
YY and Seto openly comunicated with eachother anyway and so did L&U, the receiver trick wasn't in the manga so i don't even get the point of L&U "cheating"
5) 11° duel, Malik!Joey vs Yugi/YY, absolutely everything about this duel is illegal, cards, death threats, do i even need to list them all?
6) 12° duel: Yami Bakura vs Bonz/Ghost, Bakura won but he made a duel a Shadow Game and sent his opponent to Hell which i'm sure it's again the rules even if it's not specified
7) 13° duel: Mai vs Magnus: Mai won but Magnus used a real stunt actor to replace one of his monsters in Solid Vision which i doubt it's something Kaiba would allow
8) 14° duel: YB vs YY, YY won but Rishid/Odion (disguises as Marik) interrupts the duel and talks with him
9) 15° duel: Joey vs Odion, Joey won but Odion used a fake Winged Dragon of Ra
10) 16° duel, Yami Marik vs Mai, YM won, but again, he made the duel a Shadow Game
