Is there an opposite feature to this?
Show only when a field entry is X, but hides when there is any other entry?
There are other techniques you could likely use...
...or you could use the Hide Object When feature and have the calculation be something like
FieldA ≠ X
Without knowing more about your solution and what you are trying to do, it sounds like you could still use the Hide Object When feature in some capacity.
Just use the negated condition:
Hide if =
Self ≠ "x"