General dislike or repugnance:
* Dislike
* Antipathy
* Repugnance
* Loathing
* Abhorrence
* Detestation
* Disdain
* Contempt
Strong dislike or avoidance:
* Avoidance
* Shunning
* Eschewing
* Abhorring
Specific to particular things:
* Allergy
* Sensitivity
* Intolerance
* Repulsion
The best synonym for "aversion" will depend on the context and the specific meaning you want to convey.