morbid curiosity
A rare noun for an unhealthy fascination with the bizarre, grotesque, or cruel. Often used in contexts of crime, horror, or psychological analysis.
He was investigating the details of the case out of morbid curiosity.
Compound of 猟奇 (りょうき, 'seeking the bizarre') and 心 (しん, 'mind/heart'). The exact historical derivation is uncertain, but the word follows a standard Sino-Japanese compounding pattern.