What's a good adjective for "possessing integrity"? [duplicate]

As suggested in the following usage note by M-W:

There is no adjective form of integrity. You could use another adjective with a similar meaning, such as honorable, instead.

Alternatively, you could use the noun integrity in a sentence like this,

• “She is a woman of integrity.”

"A man/woman of integrity" is a common expression, and others will definitely understand it.

An adjective you may use is upstanding:

marked by integrity - an upstanding businessman

As for integrous, its usage is very uncommon as shown in Google Books:

(rare) Having or characterized by integrity

Usage notes:

In common usage, integrity is much more common than its adjectival form, integrous. Most speakers and writers opt for an etymologically unrelated synonym — such as honest, decent, or virtuous — when trying to express an adjectival equivalent of integrity.

(yourdictionary.com)

My suggestion for an adjective is

The most principled person I've ever met.

Examples may be found at Oxford dictionary.