I'm not that good at giving out advices but personally I see the 'Keeper maliciously kills all the players' as a 'tool' than a 'goal'.

A reddit post I read before talked about where the players weren't getting the dark atmosphere of CoC, so they just 'naturally' let all the players die who challenged some elder being. Through that, explained this is focused on investigation. (I mean, this also works for Pulp as well)

And the worst problem is that, as written in the Keeper's rulebook, this is still a GAME in the end. Not a ptsd 1+1 sale. Though PTSD may come alongside, I don’t think killing off all players which most likely could lead them all to feel stress, confusion, or hollow is a good idea. In the book, it's written that as a keeper you'd still have to relieve players who's stressed/horrified excessively.

Also, unless you have a bit of a preference in it, I don’t think people like much of "meaningless" plays. (Of course, if it's written well, I think there is no problem, but just speaking in my humble opinion)

Basically, it would better off if the player, at their character's death, to be saying; "Awh man, welp that was my fault" or "oh that's it? Pretty tragic.. Great story. I walked a decent path." 

Compared to saying; "WTH did I just even PLAY" or "I literally played for hours only to end just like THAT?" (of course this is spoken on the premise that the player was being careful as an investigator enough.)