Entry 2 senses Webster, 1913

Pestilential

· Pes·ti·len·tial · IPA /ˌpɛstɪˈlɛnʃi.əl/

01 a. Having the nature or qualities of a pestilence.

1.
Having the nature or qualities of a pestilence.
2.
Hence: Mischievous; noxious; pernicious; morally destructive.
“So pestilential, so infectious a thing is sin.” — Jer. Taylor.