Someone who is fighting mad, perhaps a crazed fighter who has no thought for his own health and well being.
Dogs engaged in attack can indeed exhibit this kind of no-holds-barred viciousness, so perhaps it is apt. George Orwell classes this term, along with others “peculiar to Marxist writing.�? He included “lackey�? and “petty bourgeois�? in this category. (Orwell, George. 1946. Politics and the English Language. In In Front of Your Nose, 1945-1950, edited by I. S. O. Angus. Boston: David R Godine.)