Ie Feuds that were initiated by one celebrity but the other person just COMPLETELY paid them dust and NEVER responded to the feud at all. Eg Taylor has never @'d or evenly shadily posted about Demi at all, but Demi is still obsessively posting messages all over the internet about Taylor.
Katy v Taylor doesn't count because Katy did post several tweets referencing it all, even if she never directly @'d Taylor (she was afraid to).