None, or almost none.
There are two different prefixes here.
The familiar one means "not": unhappy, unfair, unusual, unseen.
The other prefix is rarer. I'll quote the American Heritage Dictionary, 4th edition:
1. To reverse or undo the result of a specified action: unbind.
2a. To deprive of or remove a specified thing: unfrock.
b. To release, free, or remove from: unyoke.
3. Used as an intensive: unloose.