There is no clear antonym listed in thesaurus but it could be reverse agent.
An agent of change might be a "catalyst." Some antonyms of catalyst are:
There is no actual opposite for the noun agent (representative, envoy).
An agent is someone that represents another person or acts on their behalf. An antonym is a word that means the opposite of another word. Antonyms for the word agent include customer, client, and courtier.
A conduit is a tube used as a passage for liquids, or in its broader sense an agent of communication etc. There is no antonym.
The definition of emissary is an agent sent on a mission to represent or advance the interests of another. I am unable to find an antonym.
A synonym for transform is change. An antonym for transform is preserve.
a synonym is change and antonym is non-change
in the context of organisation change and development, the antonym of scalability is: rigidity, inflexibility, the inability to change to meet changing circumstances within or from without the organisation
An agent of change is someone or some thing that facilitates change of some sort.
A change agent is an event, organisation, material thing or, more usually, a person that acts as a catalyst for change. In business terms, a change agent is a person chosen to bring about organisational change. Corporations often hire senior managers or even chief executives because of their aboility to effect change. Use in a sentence - Mr. Farnsworth is considered a change agent for his organization.
A sudden and random change of subject with no segue is a non sequitur.
A sentinel guards against enemies getting in, so an antonym might be a mole, meaning an enemy agent operating "underground."
hmmm