RWBY: Grimm Eclipse

With all of the character specific campaign completions, you only need to finish the final mission, "Final Exam", to count for the achievement. That being said, if you plan to do the final mission solo then I highly recommend being levels 8-10. It's a nightmare, and even worse if you are playing as Ruby or Yang. You do though need to play through the entire campaign to be able to pick the final level through level select, though as you need to complete the game solo then that shouldn't be an issue.