Maybe I'm doing something wrong or the game has been changed, but I can't get the result through the described algorithm.
1. I'm running a local game.
1.1. refuse to restart under steam. Choose Offline.
1.2. get an empty profile, create a new lvl 1 hero (for some reason I can't create a veteran).
1.3. create a new match in the History mode (other modes are not allowed).
2. start the game from steam.
2.1. The veteran can't join the local baby, so I'm creating a new level 1 hero.
3. join to the local match.
4. press Alt-F4 when a band of bloodstains begins to grow at the bottom against the background of two leaflets.
Run steam game again, start plain story and check there counter - it remains unchanged. What I do wrong?

Can confirm that this works and it allowed me to get the final 4 counts I was missing.

I had the same character joining itself between local and Steam version.

Note that I had to switch around characters and even create an entirely fresh character for it to progress till the end, but it worked.

Awesome guide!

Well in this folder there are 6 launchers so if you fuck up with 1 use can still use other 5 and it will still work.
Also if you have good procesor you can farm kills for The Grim Reaper himself ;)

Tried this solo with new characters and it works. Thanks for this, I've been looking to get this achievement for a while.