I've seen it in Latin, and not too many other languages, would it be “niente dei non re?”
As far as I have seen searching on Google, "No Gods, no kings, only man" is a quote from the videogame "Bioshock"; I think it states the absolute value of freedom and that every man is the supreme ruler of himself and does not need authorities (moral or political) tho whom delegate this power. Possibly a reference to the anarchist labour slogan "No God, no master".
Possible Italian translations could be:
Niente dei, nessun re
Né dei, né re
or slightly different:
Nessun dio, nessun re