A popular slang word meaning (roughly): "it will not survive!", "completely destroyed!", "it's nearly a corpse!". Usage: [noun in Dative] + кирдык (you can swap the word order). Synonyms: (warning! contains mat) конец, капут (more or less polite), копец, пипец, песец (euphemisms to a mat word), пиздец (select to make it visible).

E.g.: you can say it to your enemy before the battle: Тебе кирдык!

BTW, what's the English equivalent slang word or expression for this?

PS Actually, "песец" is this guy :
(Alopex lagopus, arctic fox)
But it just sounds somewhat similar to the mat word.

One more fact: the American movie "Kick-Ass" due to some reason was translated into Russian as "Пипец".