Blasphemous Act is the first such card that comes to mind, offering a potential nine points of damage despite effectively being anything but a nine cost spell
In terms of notable staples that are worth being happy about, theres Sakura-Tribe Elder, Cultivate, and the Signets
That means you can get free cards until something big arrives like Ulamog or a Colossus
Cards are usually not banned for power level reasons, and the last time it happened was Lurrus Of The Dream Den prior to the nerf to the companion mechanic
As of August 2024, the highest-selling Time Walk is a Limited Edition Alpha example that realized $63,000 in an April 2023 Fanatics Collect Premium Auction
So it feels like because her power is 5, what seems like a really cool ability actually washes out in actual gameplay