Yu-Gi-Oh! 10 Powerful Cards So Good They Were Banned!
8. Tempest Magician
Tempest Magician is a Lv6 synchro monster that required any tuner and 1 or more 'spellcaster' monsters who's levels added up to 6 to summon. It's effect allowed it to discard cards from the hand in order to place 'spell counters' on cards you control, and then inflict 500 points of direct 'burn' damage to your opponent for each spell counter on the field by removing them.
Although the card was released back in 'Crossroads of Chaos' back in 2008, it never got much play outside of the occasional rogue deck as amassing spell counters was relatively difficult, and it was often not worth the pay off to deal only 500 damage per counter. However, with recent pendulum 'Magician', 'Endymion' and 'Mythical Beast' support alongside 'Electrumite' it allowed one to search out tuners, amass spell counters and summon Temptest and inflict upwards of 10 000 damage on a players first turn.
Even outside of pendulum spell counter based decks, Tempest became abused with the likes of 'Isolde', 'De-Synchro' & 'Magikat' loops to consistently summon and burn your opponent over and over again until they lose or forfeit, forcing Konami to ban the card.