The Key Here is stealth. Narcissistic criticism is masked as honesty. When honestly who really wants another to "however kindly" tell them how they fall short. Their criticism is not intended to be constructive but rather to ever so insidiously devalue you.
Their version of "love" is based on conditions you must meet. Listen closely as they reveal this in every "helpful criticism," every "concern" for your well-being, and every argument where supposedly resolved issues never cease to resurface.
One of the biggest signs and traits of narcissism is Hoovering. This technique usually appears after months, even years of no contact. Narcissists will try every trick in the book to get you back into the codependent cycle.