If "haunt" means to visit or appear frequently in a place:
* Leave
* Depart
* Abandon
* Disappear
If "haunt" means to trouble or worry someone:
* Comfort
* Soothe
* Reassure
* Calm
If "haunt" means to be a persistent memory:
* Forget
* Erase
* Dismiss
* Suppress
Ultimately, the best opposite for "haunt" will depend on the specific context in which it is used.