Coming to exist is always a harm. Or so argues David Benatar in his provocative book, Better Never to Have Been.
A central pillar of Benatar's defense of this offputting 'anti-natalist' thesis is what he calls the asymmetry argument (BNHB, p. 30):
Pleasure benefits us and pain harms us.
(1) The presence of pain is bad.
(2) The presence of pleasure is good.
So far, pleasure and pain are symmetrical in their goodness and badness. But they are not symmetrical with respect to their absence. More specifically:
(3) The absence of pain is good, even if that good is not enjoyed by anyone, but
(4) The absence of pleasure is not bad unless there is somebody (an actual somebody) who is deprived by its absence.