I know what you're thinking. "There's no such thing as an objectively best card, otherwise everyo--".
Well you're wrong! The perfect card exists! And it's Thalia, Guardian of Thraben.
a) Name a format. Go ahead. You can play her to success there.
b) Despite a), she remains affordable thanks to plentiful printings!
c) Despite a), she is not an oppressive presence in any format.
ℹ️ Note
I'd put something here but that sounds like a lot of effort to prove so, like, just trust me on this one.
d) She's good pressure in the early game without unreasonably accelerating the formats she's in.
e) She keeps a check on non-creature combo decks, like Storm.
f) She's not an auto-include in every deck that plays white, because the effect affects the player controlling Thalia as well.
g) She's got a variety of phenomenal artwork.
Look at these! Incredible art all around.
Alright, that's all I got. Thanks for coming to my TED talk!!