3 adjectives to describe underminer

Do not blush at the association; your views have been the same; and the subtle underminer of man's best comfort in the principles of his religion, is even more criminal than him who prohibits the external exercise of it.

And I fell asleep thinking that parents have a duty to children greater than children to parents, and they who do not fulfil their responsibility in this respect are as bad in their morals as a debauchee, corrupt the community as much as a thief, and are among the ablest underminers of their nation.

That it was not their care to countenance, encourage, entrust, and employ, such only as from their hearts did affect and mind God's work; but the hearts of such, many times had been discouraged, and their hands weakened, their sufferings neglected, and themselves slighted, and many who had been once open enemies, and always secret underminers, countenanced and employed.

3 adjectives to describe  underminer