No, "weakened" is not an adverb.

The word "weakened" is a verb.

The antonym of weakened is strengthened.

It is weakened by CFC's. They react with ozone and deplete it.

Basically the Roman army was weakened by inaction which led to lack of discipline.

Basically the Roman army was weakened by inaction which led to lack of discipline.

Basically the Roman army was weakened by inaction which led to lack of discipline.

Basically the Roman army was weakened by inaction which led to lack of discipline.

Basically the Roman army was weakened by inaction which led to lack of discipline.

Basically the Roman army was weakened by inaction which led to lack of discipline.

Basically the Roman army was weakened by inaction which led to lack of discipline.

Basically the Roman army was weakened by inaction which led to lack of discipline.

Basically the Roman army was weakened by inaction which led to lack of discipline.

The popular support for Cold War theories was weakened by the outcome of the Vietnam war. It had also weakened the moral of the US military.