* Good: This is the most general opposite.
* Wonderful: This implies something more than just good; it's amazing or fantastic.
* Delightful: This suggests something pleasing and enjoyable.
* Superb: This suggests something excellent and impressive.
* Fantastic: This is similar to wonderful, but often used more informally.
* Amazing: This implies something that is astounding or incredible.
* Terrific: This implies something great or excellent.
* Splendid: This implies something magnificent or impressive.
The best opposite word will depend on the specific situation and what you are trying to convey.