Merriam:
Vitiate:
1. : to make faulty or defective : impair
the comic impact is vitiated by obvious haste —William Styron
2: to debase in moral or aesthetic status a mind vitiated by prejudice
3: to make ineffective fraud vitiates a contract
My Definition:

Debasement of; impairment of, corruption of
“Her knowledge of the lie led to the vitiation of their council”
“The vitiation of his morals was due to the chaos he witnessed early on”