A blood feud is a long-lasting, bitter disagreement between two or more groups of people, particularly family groups. Blood feuds often involve members of each group murdering or fighting with members of the other.
blood feud in British English
noun
a feud in which the members of hostile families or clans murder each other
blood feud in American English
feud1 (sense 1)
Examples of 'blood feud' in a sentence
blood feud
Officials said that other witnesses were scared to come forward for fear of becoming embroiled in a family blood feud.
Times, Sunday Times (2011)
I think European club football could do with a blood feud or two.