As long as both the question and its answer(s) heed the general Code of Conduct, I think there is no problem.
There is inherently nothing wrong about asking a question like that, as long as you exclude potential filter keywords, explicit imagery or links to potentially harmful websites.
In this particular case, the Adults Only rating is used for the PC version of Manhunt 2, probably since one of the major differences is that "the executions are uncut and uncensored" *. I don't think phrasing it like that violates the CoC or is particularly disturbing to the gaming community.
One of the differences between the Mature and the Adults Only ESRB ratings are "prolonged scenes of intense violence" (source)