General Opposites:
* Misunderstand
* Misinterpret
* Fail to grasp
* Not understand
Specific Opposites:
* Ignore: If you are talking about the act of paying attention to something.
* Disregard: If you are talking about the act of considering something.
* Reject: If you are talking about the act of accepting an idea or explanation.
The best opposite for "comprehend" will depend on the context of the sentence.