Classical narcissists do not enjoy wounding others - but they do enjoy the sensation of unlimited power and the validation of their grandiose fantasies when they do harm others or are in the position to do so. It is more the POTENTIAL to hurt others than the actual act that turns them on.
Even the official termination of a relationship with a narcissist is not the end of the affair. The Ex "belongs" to the narcissist. She is an inseparable part of his Pathological Narcissistic Space. This possessive streak survives the physical separation.
Thus, the narcissist is likely to respond with rage, seething envy, a sense of humiliation and invasion and violent-aggressive urges to an ex's new boyfriend, or new job (to her new life without him). Especially since it implies a "failure" on his part and, thus negates his grandiosity.
But there is a second scenario:
If the narcissist firmly believes (which is very rare) that the ex does not and will never represent any amount, however marginal and residual, of any kind (primary or secondary) of Narcissistic Supply - he remains utterly unmoved by anything she does and anyone she may choose to be with.
Narcissists do feel bad about hurting others and about the unsavoury course their lives tend to assume. Their underlying (and subconscious) ego-dystony (=feeling bad about themselves) was only recently discovered and described. But the narcissist feels bad only when his Supply Sources are threatened because of his behaviour or following a narcissistic injury in the course of a major life crisis.
The narcissist equates emotions with weakness. He regards the sentimental and the emotional with contempt. He looks down on the sensitive and the vulnerable. He derides and despises the dependent and the loving. He mocks expressions of compassion and passion. He is devoid of empathy. He is so afraid of his True Self that he would rather disparage it than admit to his own faults and "soft spots".
He likes to talk about himself in mechanical terms ("machine", "efficient", "punctual", "output", "computer"). He suppresses his human side diligently and with dedication. To him being human and survival are mutually exclusive propositions. He must choose and his choice is clear. The narcissist never looks back, unless and until forced to by life's circumstances.
All narcissists fear intimacy. But the cerebral narcissist deploys strong defences against it: "scientific detachment" (the narcissist as the eternal observer), intellectualising and rationalising his emotions away, intellectual cruelty (see my FAQ regarding inappropriate affect), intellectual "annexation" (he regards others as his extension, property, or turf), objectifying the other and so on. Even emotions that he does express (pathological envy, rage) have the not wholly unintended effect of alienating rather than creating intimacy.
The narcissist initiates his own abandonment because of his fear of it. He is so terrified of losing his sources of Narcissistic Supply (and of being emotionally hurt) that he would rather "control", "master", or "direct" the potentially destabilising situation. Remember: the personality of the narcissist has a low level of organization. It is precariously balanced.
Being abandoned could cause a narcissistic injury so grave that the whole edifice can come crumbling down. Narcissists usually entertain suicidal ideation in such cases. But, if the narcissist had initiated and directed his own abandonment, if it is perceived as a goal he set to himself - he can and does avoid all these untoward consequences. (See the section about Emotional Involvement Prevention Mechanisms in the Essay.)
The narcissist lives in a fantasised world of ideal beauty, incomparable (imaginary) achievements, wealth, brilliance and unmitigated success. The narcissist denies his reality constantly. This is what I call the Grandiosity Gap - the abyss between his sense of entitlement grounded in his inflated grandiose fantasies - and his incommensurate reality and meagre accomplishments.
The narcissist's partner is perceived by him to be merely a Source of Narcissistic Supply, an instrument, an extension of himself. It is inconceivable that - blessed by the constant presence of the narcissist - such a tool would malfunction. The needs and grievances of the partner are perceived by the narcissist as threats and slights.
The narcissist considers his very presence in the relationship as nourishing and sustaining. He feels entitled to the best others can offer without investing in maintaining his relationships or in catering to the well-being of his "suppliers". To rid himself of deep-set feelings of (rather justified) guilt and shame - he pathologizes the partner.
He projects his own mental illness unto her. Through the intricate mechanism of projective identification he forces her to play an emergent role of "the sick" or "the weak" or "the naive" or "the dumb" or "the no good". What he denies in himself, what he is loath to face in his own personality - he attributes to others and moulds them to conform to his prejudices against himself.