Was recently looking for emojis to indicate success/failure in a CLI and for a checkmark, you have these options: ✔️✅☑️

I figured, I'd take the one with green background for best visibility.

Now for an X-emoji, we've got this one: ❌
But isn't there one with a background, too?
Well, yes, there is, but: ❎

(That's displayed with a green background on most systems, in case it's showing differently for anyone.)