Kanske "säga upp bekantskapen"?

"raderade honom/henne ifrån min vänlista"

ovän

otrevlig, som tex. he is unfriendly..

I must say that I had never heard the word "unfriend" until Facebook came along and I don't believe it is ever properly used outside a social networking site, since it was invented for that purpose and there is no such word in everyday language (as far as I know). So you're looking for a non-social-networking translation to a social-networking-only word.

Surely this can’t be the first time a word gets taken out of its original context to be used elsewhere. Isn’t this one of the grander paths a language follows in transforming/evolving? So although the point of using a non-social-networking etc. is both observant and correct, it leaves me wondering – what would a correct translation sound like? The word is here and it is used – a lot.