Ill go over a few examples of why some specific cards have been banned: Treasure Cruise + Dig Through Time [mtg_card]Treasure Cruise[/mtg_card] and [mtg_card]Dig Through Time[/mtg_card] are examples of cards that were individually too powerful for Modern (amongst other formats)
As if all that somehow wasnt enough, Ondu Spiritdancer even has serious combo potential in MTG Commander
Entropic Uprising Next up, we have the general I have most personal experience with: Yidris, Maelstrom Wielder
But Kristen, you may ask, what about my fair Muldrotha deck? Well, most players might quip that theres no such thing as a fair Muldrotha deck, and to this day, I havent played against one though I am always open to having my mind changed
This can be turned to into an upside with Metamorphic Alteration, making your opponent lose the game on the spot if they have a creature, which becomes a copy of this demon but without the counters