0 used to say that something is sad, disappointing, or has a bad effect:
Journalists may enter the danger zone but unfortunately we cannot guarantee their safety.
Unfortunately we can't come this evening after all.
We tried to get tickets, but unfortunately they were already sold out.
Unfortunately the plane has been delayed - the new departure time is 16.20.
The analysis of the qualitative data appears, unfortunately, to have been somewhat superficial.
Unfortunately, rigorous scientific data are lacking on the efficacy and effectiveness to justify medical practice.
Many other adverbs (as interestingly, frankly, clearly, luckily, unfortunately) are similarly used; most are so ordinary as to excite no comment or interest whatsoever.