A paraphilia is a condition in which a person's sexual arousal and gratification depend on fantasizing about and engaging in sexual behavior that is atypical and extreme. A paraphilia can revolve around a particular object (children, animals, underwear) or around a particular act (inflicting pain, exposing oneself). Most paraphilias are far more common in men than in women. The focus of a paraphilia is usually very specific and unchanging.
A paraphilia is distinguished by a preoccupation with the object or behavior to the point of being dependent on that object or behavior for sexual gratification.
Paraphilias include sexual behaviors that society may view as distasteful, unusual or abnormal. In descending order, the most common are pedophilia (sexual activity with a child usually 13 years old or younger), exhibitionism (exposure of genitals to strangers), voyeurism (observing private activities of unaware victims) and frotteurism (touching, rubbing against a nonconsenting person), while fetishism (use of inanimate objects), sexual masochism (being humiliated or forced to suffer), sexual sadism (inflicting humiliation or suffering) and transvestic fetishism (cross-dressing) are far less common. Some of these behaviors are illegal and those who are under treatment for paraphilias have often encountered legal situations surrounding their behaviors. There is also a category called Paraphilia Not Otherwise Specified to cover paraphilias not falling into the already named diagnoses such as those involving dead people, urine, feces, enemas and obscene phone calls.
Even when practiced in reality, it seems to me the victims of necrophiliacs do not suffer any psychological harm or physical discomfort.
So I think it's actually the best paraphilia that involves (parts of) humans as objects of sexual lust. Provided you don't kill them for the purpose first ;-).