"Mortal Kombat vs DC Universe: Sonya's Fatality 1" is a video on the subject.

A Fatality is an end-of-round move that can be performed when the opponent's health is zero.You will have around 5 seconds to perform a Fatality, or let the round end, after you finish the last attack or combo.

Is DC Universe compatible with Mortal Kombat?A major DC superhero title is now compatible with the Xbox One.The team at NetherRealm Studios took that familiar skeleton and retooled it for a brand new fighting experience instead of copying and paste DC characters.

Darkseid can be unlocked by completing the DC side of story mode.The side of story mode can be unlocked by completing it.