Suicide
Suicide contradicts the natural inclination of the human being to preserve and perpetuate his life.
It is gravely contrary to the just love of self.
It likewise offends love of neighbor because it unjustly breaks the ties of solidarity with family, nation, and other human societies to which we continue to have obligations.
Suicide is contrary to love for the living God.
Source: Catechism of the Catholic Church (Vatican.va)