I encounted this problem recently. Wonder how people make of it.
This is from the Encomium of Helen. Gorgias is here putting forward this fourth argument that it is unfair to accuse Helen if she was awe-stricken by Eros, i.e. by the vision of Paris' bodily beauty, a force to which everybody else is also liable.
ἰσχυρὰ γὰρ ἡ συνήθεια τοῦ νόμου διὰ τὸν φόβον ἐξωικίσθη τὸν ἀπὸ τῆς ὄψεως, ἥτις
ἐλθοῦσα ἐποίησεν ἀμελῆσαι καὶ τοῦ καλοῦ τοῦ διὰ τὸν νόμον κρινομένου καὶ τοῦ ἀγαθοῦ τοῦ διὰ τὴν νίκην γινομένου.
(Gorgias, Encomium of Helen 16, TLG text from Diels & Kranz)
Admittedly Diels introduced into the really corrupted text a few emendations, some of which his own (e.g συνήθεια for the transmitted "aletheia"), some by other scholars (Reiske's ἐξωικίσθη for "ei)swki/sqh", Bekker's ἀμελῆσαι for "a)smeni/sai", and Blass' νίκην for "di/khn"), but as the text stands without a dagger in Diels, I expect it to make grammatical sense. But as it is, I have difficulty translating that first ἰσχυρὰ: it stands in predicative position, but the only way I can deal with it is thus,
"for the habit of the custom, though being forceful, is driven (gn. aor.) out of home by the fear which comes from the vision, which upon its arrival causes (sc. people) neglect both the beauty which has been determined by the usage/custom, and the good which comes about through the victory."
The problem is that there seems to be no such monstrocity as a predicative "concessive adjective" in either Smyth or K & G (auf Deutsch ein "einräumendes adjektiv"). Or do people have other suggestion for translation?