I mean, I think I know what you are getting at, but how the hell are you going to have a plot if you have some crazy guy rampaging all over some friendly world? It seems like you would just put something dark in something light for the sake of it.
From this, I'm guessing you don't want those "cynical" type of stuff people were mentioning. I think what you're trying to say is a "what if something our guy basically sees some other people talk about power of friendship and love, and then beat the shit out of him and calls it bullshit."
The reverse of what you're asking has been done (Instead of guts in sailor moon, its like sailor moon in Beserk, I guess) in which certain perception of cute genres are taken in dark direction, but I don't think that's what you're looking for.
I'll say that what you want might not exist, but there is a shitload of anime there, so I don't know. I'll say that I'm pretty sure there would be some manga that fits what you're looking for.