General opposites:
* Delightful
* Wonderful
* Excellent
* Superb
* Amazing
* Fantastic
More specific opposites:
* Joyful (if the context is emotional)
* Pleasant (if the context is about experience)
* Hopeful (if the context is about future outlook)
* Promising (if the context is about potential)
* Safe (if the context is about danger)
For a more precise answer, please provide the context of the word "dreadful".