Wizards of the Coast define Game Changers as cards that dramatically warp Commander games, allowing players to run away with resources, shift games in ways that many players dislike, block people from play, efficiently search for their strongest cards, or have Commanders that tend to take away from more casual games
Original Planechase was released back in 2009
Ah, yes, Spacegodzilla, Death Corona
Simic Ascendancy Like Revel in Riches, WotC keeps printing better cards that come with +1/+1 counters or interact with them, so its not hard to go off with Simic Ascendancy
Illustrated by Alan Rabinowitz Standard Not Legal Alchemy Not Legal Pioneer Not Legal Historic Not Legal Modern Not Legal Brawl Not Legal Legacy Legal Comp