I tried stretching this one and saying "Neha's cat is very naughty." It was rejected, and I'm sure there's a word in Hindi that actually carries the nuance of "naughty", so I can accept that this should be translated straight as "bad" like the lesson indicates.
If that's not the case and I was actually (arguably) right, somebody let me know.
Only in certain contexts (if you are talking to a very young child for example). बदमाश actually has more negative connotations otherwise.
शरारती or नटखट is a closer translation to naughty.