Just kill 100 Succubus. Go to kill Succubus game mode to do it faster. Not needed to be done in one try. so just spam autoattack and camp the spawns.

If any achievement didn't unlocked during the gameplay. Delete the savegame and then repeat.

Files can be deleted in this path: \AppData\Local\HnH\Saved\SaveGames (you can open the appdata folder typing %appdata% at windows search bar)

just delete all files in that folder.