Some are more egregious than others
Despite its Special Art card being removed, this rare Mewtwo is one to watch out for and a must-have on this list
These creatures typically care about the graveyard and/or creatures in some fashion: Maybe they cast spells from the graveyard or reward you for filling the graveyard, maybe they recur cards
Their card stock is thicker, their backside features a glossy finish, their color are a little darker, and their printing style does not show the characteristic pattern of dots, but is completely undiscernible
If we were to rank these Megas based on the modern Expanded Format, M Charizard-EX (X) from Flashfire would be on the list due to its heavy use in Regidrago V-Star decks, but in the XY Format, it was rarely even seen due to how slow it was to set up
At that point hes pretty much unplayable, even before you account for the fact that he only protects humans and artifact creatures