What is the opposite of a "false positive"?
There is not simply one "opposite" to a false positive; Wikipedia has a good summary of the types of statistical errors.
Your question doesn't make sense, logically: the data contains four things, in this context:
- true positives
- false positives
- true negatives
- false negatives
If we remove the false positives we're left with
- true positives
- true negatives
- false negatives
This isn't "the opposite of false positives". It's just the data minus the false positives.