Mutilation is the process of injuring or ruining something (or someone), like your little brother's mutilation of the science project you stayed up all night finishing. You can also use the word for the result of this extreme kind of injury.
When a person or an object has been altered or damaged in a permanent way, that's a mutilation. The mutilation of your favorite teddy bear by the family dog when you were little may have scarred you for life. Movie monsters sometimes exhibit mutilations (like missing eyes or limbs), and sometimes threaten mutilation to others (by wielding weapons or sharp teeth). The root word of this gory noun is the Latin mutilare, "to cut or lop off."