If you’re still looking for last-minute Halloween costumes — play along with me here, huh? — might I suggest what might possibly be the scariest one of all? Dress up like a (gasp!) Men’s Rights Activist, like the fellow above, a real-life MRA cosplayer I found on STFU Assholes.
If you’re looking for more MRA costume ideas, I suggest perusing the pictures here. (Warning: these are actual MRAs.)