inveterate

Firmly established from having been around for a long time; of long standing.

Near-synonyms: deep-rooted, ingrained, ineradicable, indelible, radicated, chronic, permanent

an inveterate disease

Having had a habit (usually a bad habit) for a long time.

Near-synonyms: hardened, chronic, dyed-in-the-wool

an inveterate idler;   an inveterate gambler;   an inveterate smoker

Malignant; virulent; spiteful.

A man of mild manners can form no idea of inveterate revenge or cruelty[…]

1765–70, Henry Brooke, The Fool of Quality; or, The History of Henry, Earl of Moreland This his lordship perused with a countenance, and scrutiny, apparently inveterate.

To fix and settle after a long time; to entrench.

"the vulgar conceived that now there was an end given, and a consummation to superstitious prophecies, the belief of fools, but the talk sometimes of wise men, and to an ancient tacit expectation which had by tradition been infused and inveterated into men's minds."

"none of these Princes do use to maintaine any armies together, which are annex'd and inveterated with the governments of the provinces, as were the armies of the Roman Empire. "