Very simple achievement that's tied to the campaign if you're following it. You must defeat Captain Vor in the Mercury region / Tolstoj, Iliad mission and extract alone or with other players.
But be warned: Probably like the other boss related cheevos. you must play the entire mission from the very start to the end! if you match make in a game in progress, the achievement will not pop and you're forced to do it again! (at least that's what happened to me)
Below is a youtube vid of the fight itself by scorpioofshadows