V Not Cupcakes, think Rocket to Insanity.

Rainbow Dash is having constant Nightmares about (what else Cupcakes), and when Pinkie presses Dash in a non-threatening manor Dash just snaps and kills Pinkie, before she'd give Pink the "chance".



Only thing is Pink (in RtI), wouldn't kill Dash.



As far as these Stories go I guess this was a close as Dash ever got to the good end.