Green’s Dictionary of Slang

fighty adj.

aggressive.

1844		G.W. Kendall Narrative of Texan Santa Fe Expedition I 133: Captain Caldwell [...] remarked to his men, in a low tone and in English, that ‘these fellows looked ugly and fighty’.
1888		W.B. Churchward Blackbirding In The South Pacific 108: I don’t want no rowdy chaps in my ship; they annoy me, and then I get bad and fighty.