G4258–προαμαρτάνω–proamartanō

lest again when I come my God should humble me before you, and I should mourn for many of them that have sinned heretofore, and repented not of the uncleanness and fornication and lasciviousness which they committed.

προημαρτηκότων proēmartēkotōn “having sinned before”

I have said beforehand, and I do say beforehand, as when I was present the second time, so now, being absent, to them that have sinned heretofore, and to all the rest, that, if I come again, I will not spare;

προημαρτηκόσιν proēmartēkosin “having sinned before”