People forced to participate in games involving fighting to the death, torture games, etc. for the entertainment of others, or the people watching them.
A lot of these have corrupted/apathetic MC’s! If you want more like that, try this list:
http://www.mangago.me/home/mangalist/1057049/ 
Messages
Oh my god thank you so much for making this list and taking the time out of your day I love this kind of story look with torture killing games but I can almost never find anything like this so once again thank you so much you're my life saver(๑•ㅂ•)و✧
Of course! I’m glad I could help & that we have similar taste.