saeviter
From LSJ
μοῦνοι Ἑλλήνων δὴ μουνομαχήσαντες τῷ Πέρσῃ → alone of all Greeks we met the Persian singlehandedly, alone of all Greeks having fought singlehanded with the Persians
Latin > English (Lewis & Short)
saevĭter: adv., v. saevus.
Latin > French (Gaffiot 2016)
sævĭtĕr (sævus), avec rigueur : Pl. Ps. 1290 ; Enn. Scen. 180 ; 307.