Baneful, a.
Having poisonous qualities; deadly; destructive; injurious; noxious; pernicious. "Baneful hemlock." Garth. "Baneful wrath." Chapman. -- Bane"ful*ly, adv. --Bane"ful*ness, n.
Shades of meaning
Fernald has no entry of its own for baneful; he lists it under pernicious.
He lists it without comment; the entries above explain its neighbors.