undermine

To weaken by wearing away a base or foundation.

To weaken, injure, or impair, often by degrees or imperceptibly; sap.

To dig a mine or tunnel beneath.

To form a mine under; sap; render unstable by digging or wearing away the foundation of; make an excavation beneath, especially for the purpose of causing to fall, or of blowing up.

Figuratively, to subvert by removing clandestinely the foundation of; injure by invisible, secret, or dishonorable means.