General Antonyms:
* Respect
* Admire
* Approve
* Agree
* Praise
* Revere
* Esteem
* Acknowledge
* Accept
Antonyms specific to the context of "scoffing" at something:
* Believe
* Trust
* Take seriously
* Heed
* Consider
* Appreciate
The best antonym will depend on the specific context in which "scoff" is being used.