LAST EDITED ON Jan-26-18 AT 07:27 AM (EST)
 
Heh, sounds a little like SyFy's show "Happy," where a hard-boiled, dark, violent ex-police officer turned hitman (played by SVU's Christopher Meloni) is visited by a little girl's imaginary friend (a flying donkey unicorn voiced by Patton Oswalt) to help save her from a Very Bad Santa.

It's about as over-the-top and violent as you think, only more so. :) Based on a Grant Morrison comic book, I think.

Edit: Sorry, a bit of a derail, I shouldn't post so early in the morning. The over-talkative familiar made me think of this.