I watched it a little while ago, upon urging.
I was familiar with the ending based on internet memes and looking of yandere on Wikipedia. I wasn't expecting... well, a douche-bag's unsurpassed success with apparently witless women.
I assumed, based on the shocking response, that it came out of left field as they say. I'm not sure why, left field seems as reasonable place as any for things to come out of. Still, when it comes to shock value, something like Shigofumi had more of an impact, honestly.
I'm actually pretty disturbed with myself right now. I know people like Makoto, or who want to be, they cause me to fall into misanthropic shame spirals.