Article 5 of the Universal Declaration of Human Rights.
No one shall be subjected to torture or to cruel, inhuman or degrading treatment or punishment.
The Convention against torture and others cruel, inhuman or degrading punishments or treatments, adopted by UN General Assembly the 10 December 1984, establishes in the 1 article the following definition of torture:
“Any act by which severe pain or suffering, whether physical or mental, is intentionally inflicted on a person for such purposes as obtaining from him or a third person information or a confession, punishing him for an act he or a third person has committed or is suspected of having committed, or intimidating or coercing him or a third person, or for any reason based on discrimination of any kind, when such pain or suffering is inflicted by or at the instigation of or with the consent or acquiescence of a public official or other person acting in an official capacity. It does not include pain or suffering arising only from, inherent in or incidental to lawful sanctions.”
Torture is a crime against humanity, that’s why it’s one of the most execrable actions can be done at another human being expense.