How does the narcissist react when he realizes you no longer care?

After the initial disbelief there will usually be either

2. Extremely focused rages and backstabbing to make other people see the error of your ways.

It's good to get one of those morale-boosting, self-esteem-elevating, motivational pep talks from the narcissist. You've probably already had several of these 'talks' from the narcissist. The narcissist seems to have no conception that these "talks', punishments, silent treatments, word games, head games, rages, apologies that meant nothing, promises to change that were actually kept except the changes were always worse for you, games with rules only the narcissist knows and only the narcissist can change, being backstabbed, degraded, and insulted by the narcissist are the reason that YOU 'no longer care'.

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3. Totally ignoring you as long as you have totally disappeared from THEIR world.

10 Things That Will Happen During a Narcissistic Collapse

1. Concentrated love-bombing to make you see the error of your ways.

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The initial reaction is usually total disbelief. They think you're trying to play a “silent treatment” game on them or somehow make them 'look bad' or somehow 'ruin their day' or somehow 'hurt' their 'feelings' or somehow trying to 'control' them or somehow being'selfish', and they 'just can't believe how much you've changed'. What the hell is wrong with YOU? How could YOU be so cold and uncaring after all I've done for you/given up for you/nice as I've been to you/all I've been through for you/all I've been through because of you/how could YOU treat ME like this? Your only reaction to ME is that you "don't care.". EVERYBODY 'loves ME'. You're not even human. EVERYBODY told ME you were like that. I should have known. I've been willing to give you ONE MORE CHANCE to show some respect and care for my feelings, even though you're a worthless, inhuman, uncaring, self-centered piece of shit who nobody cares anything about but ME.

4. All of the above.

The disbelief is not in that you 'no longer care'; the disbelief is in that it's THEM you 'no longer care' FOR or ABOUT. All of those games, manipulations, rages, talks, etc. were supposed to make you 'no longer care', but it was YOU and everybody around YOU that YOU were supposed to 'no longer care' about.

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Why The Narcissist Starts Caring When You Stop

Some reading suggestions: