Love Child
One Love
I mean usually people do oh ffs, but I want to know
Oh for Fuck's sake is the long formal version. It implies everything has happened and it's bad.
Fuck Sake is the abbreviated, slightly exasperated but potentially time to avert the thing that might happen that's bad.
Example:
While searching for the dog shit smell inside the house, you discover it by stepping on it while wearing only socks.
"Oh for Fuck's Sake... you dirty bastard"
Example:
The dog attempts to shit in the front room
"Fuck sake! get out of the house you little shit."