weakener vs agent

weakener and agent both are nouns.

Word	Noun	Adjective	Verb	Adverb
weakener	Yes	No	No	No
agent	Yes	No	No	No

As nouns, agent is a hypernym of weakener; that is, agent is a word with a broader meaning than weakener:

weakener (noun)	agent (noun)
that which weakens or causes a loss of strength	the semantic role of the animate entity that instigates or causes the happening denoted by the verb in the clause
	an active and efficient cause; capable of producing a certain effect
	a businessman who buys or sells for another in exchange for a commission
	a representative who acts on behalf of other persons or organizations
	any agent or representative of a federal agency or bureau
	a substance that exerts some force or effect