"Mis-" is a prefix that usually means "wrong", "bad", or "not".
To find the opposite, you need to consider the specific word it's attached to. For example:
* Misunderstand: The opposite could be understand
* Misbehave: The opposite could be behave well or behave properly
* Misinterpret: The opposite could be interpret correctly
So, the opposite of "mis-" depends on the context and the word it modifies.