baneful

adj

Etymology: From bane + -ful.

1. Poisonous, deadly.

   “[S]ome fell ſerpent in his cave expects / The traveller's approach, batten'd vvith herbs / Of baneful juice to fury, forth he looks / Hideous, and lies coil'd all around his den.”

2. Harmful, injurious.

   “This contempt of the understanding in early life has more baneful consequences than is commonly supposed […]”