The word 'bad' is correct and usable in written English. You can use it to describe something that is not good or of poor quality. For example, "The food at the restaurant was bad.".
No deal is better than a bad deal.
But that's not necessarily a bad thing.
FIRST, the bad news.
Bad luck?
It's a bad thing.
What happened four months ago is forgotten, whether that's good, bad or indifferent.
Not so bad.
Since I tried Ludwig back in 2017, I have been constantly using it in both editing and translation. Ever since, I suggest it to my translators at ProSciEditing.
Justyna Jupowicz-Kozak
CEO of Professional Science Editing for Scientists @ prosciediting.com