Not, despite appearances, the killing of a marriage -- but see below. The murder of one's wife is uxoricide. I don't know what the gender-neutral term for killing one's spouse is, though that would be useful to have. Other family violence terms include fratricide for killing one's brother, sororicide for one's sister, patricide for father, matricide for mother, parricide for either parent, filicide for offspring, avunculicide for uncle, especially a maternal uncle, and nepoticide for nephew. All of these are from Latin relational terms, the main one from maritus, husband, from which we also get marital -- that's right, at its root, getting married meant to become or get a husband. The other part is the suffix -cide, killing, from caedere, to cut or to kill.
By the time he finished explaining my own thesis to me for the third time in as many weeks I was ready to commit mariticide.