Anything (shoujo, shounen, bl, a recommendation list etc) where MC is a canon fodder/villain and the og!protagonist is either/and/or:
The Protagonists Are Murdered by Me
NU Link: https://www.novelupdates.com/series/the-protagonists-are-murdered-by-me/
Description: Those who are...
Type - WebNovel [JP]
1. I will not become an Enemy
Author - Fuji Mitsuya (she has written a few more stuff similar)
Separate names with a comma.