banefully

from WordNet (r) 3.0 (2006)

banefully
    adv 1: in a noxiously baneful way; "this banefully poisoned
           climate" [syn: {banefully}, {perniciously}]

from The Collaborative International Dictionary of English v.0.48

Baneful \Bane"ful\, a.
   Having poisonous qualities; deadly; destructive; injurious;
   noxious; pernicious. "Baneful hemlock." --Garth. "Baneful
   wrath." --Chapman.
   [1913 Webster] -- {Bane"ful*ly}, adv. --{Bane"ful*ness}, n.
   [1913 Webster]