Sentinels of the Multiverse is part of the Steam Summer Sale
Now with Link: https://store.steampowered.com/app/337150/Sentinels_of_the_Multiverse/
You can get the base game for 3 dollars right now which includes 10 heroes, 4 villains, and 4 environment decks. Then if you end up enjoying it you can get the season passes which admittedly aren't on that much for a sale (Season 1 pass is like 30% off at 17.99 and season 2 pass isn't on sale)
However, Season 1 gets you 11 more heroes, 19 more Villains, and 11 more environments.
Season 2 isn't finished yet but currently gets you 5 heroes, 1 normal villain, 15 team-up villains, and 6 environments. There are 3 more expansions to be added.
So although a bit expensive (It is technically a card game) You do get a lot of content and a ton of replayability and each week they add a Weekly One-Shot which is a generated game that will (unless stated) always start the same to try to beat.
Oh and btw, for more replayability, each villain can be made harder through their advanced and/or challenge mechanics. Advanced adds their advanced mechanic, challenge adds theri challenge mechanic and then ultimate adds them both.