The phrase "as a hardened" is correct and usable in written English.
It can be used to describe someone who has become tough or emotionally resilient due to experiences or circumstances.
Example: "As a hardened veteran of the industry, she was not easily swayed by criticism."
Alternatives: "as a toughened" or "as a seasoned".
My friend swore by this and as a hardened alcoholic he should know.
I had imagined him as a hardened activist who had grown used to conversations about loss because he dealt with it so often.
AS a hardened newspaper reader, poring over the major papers day after day, I have gotten to the point where it takes a fair amount to startle me.
Manafort "is presented to this Court by the government as a hardened criminal who 'brazenly' violated the law and deserves no mercy.
The police took the measures in part because of Mr. Moore's history, several officials said, describing him as a hardened criminal.
One man, identified as a hardened Palestinian fighter, rushed into the church's courtyard, shooting and yelling, and was shot to death by Israeli snipers.
If the metal is hard, as in a hardened piece of steel, the loss, or reversal, of magnetization will be slow, and the sample will be useful as a permanent magnet.
Another man, "Paul," is a convicted felon, described by prosecutors as having "a hardened adherence to committing crimes and lack of remorse" after dabbling in tax fraud and money laundering.
If a group as radical and as hardened as that one were to acquire some of Syria's chemical-weapons stockpile or seized power after Assad's fall, the results might be disastrous.
The Philadelphia fan does not need them anymore as proof of a hardened soul.
We held hands, mine clammy, and we prayed as I flicked a hardened, yellow grain of overboiled rice with my toe.
