Strong:
* Contemptuous (most direct and common)
* Scornful
* Disdainful
* Sneering
* Derisive
* Mocking
* Contemptible (describes the object of contempt)
More nuanced:
* Dismissive
* Supercilious
* Patronizing
* Scathing (implies harsh criticism)
* Withering (implies a withering look or comment)
* Caustic (implies a biting or sarcastic tone)
The best adjective to use will depend on the specific context and the desired level of intensity.