Noun
an enemy who wants to kill you
Source: WordNetA pitcher has to look at the hitter as his mortal enemy. Early Wynn
One grasps incomparably more things in boredom than by labor, effort being the mortal enemy of meditation. Emil Cioran
I guess intractable right-wing ideologues are my mortal enemy. Janeane Garofalo
I see corruption as a mortal enemy for young democracies. Tsakhiagiin Elbegdorj
You have lent and not recovered; and if recovered, not so much; and if so much, not such; and if such, a mortal enemy. Portuguese Proverb
Luck is the friend of jackasses and the crazy; it's a mortal enemy of the virtuous. Sicilian Proverb