sorry for the bump of death, but there is a newer way to get the imp badge on here, and easy. It's just a glitch going around. Start a new chapter, go and get 13 (or more) kills. It can be between days or anything. Once you finish with the kills, at the upgrade scene, go to main menu, then the gladiator mode. Over the character you are using, right click and click forward. Go to any other spot open except the one you were in, in story mode. Then just simply die. It registers your kills from story mode, and it wont put you on leaderboard, but will register for the friends. Grants the badge though. I tested it a few times.