Anytime we would use this in English, we would be more likely say "it's terrible" or "it's awful" rather than just "it's bad". Those should be acceptable translations for common usage, even if not literally so.
As I understand it, רע is bad and גרוע is worse.
How about "It's worse"?
זה יותר גרוע.
AlmogL's זה יותר גרוע means "it's even worse."
Can't גרוע mean "ugly"?