Now this isn't an in depth optimization guide on getting this achievement. Since the achievement description is a bit vague, I decided to post the exact requirements and a little info for those curious.
- Complete the Campaign on Insane Difficulty
Luckily the same difficulty trick works in this game as the past ones. The person going for the achievement can play on insane, while a second player (or controller with local splitscreen) runs through on casual. This task is synonymous with the "The Night is Dark and Full of Terrors"
- Earn all Ribbons at least once
There are a total of 141 unique ribbons and a majority of them you should get while pursuing the rest of this achievement. If you’re focusing on one specific game mode I would recommend brushing up on what ribbons are specific to that so you could keep your eye out for certain opportunities. For example the “Not Today” ribbon which requires reviving every member of your team during a single round of an Execution or Warzone match. This task is synonymous with the "Chest Candy"
- Earn a Rank Placement in each mode
To earn a placement you have to complete five games of that game mode. There are six core modes and two competitive modes to play. This task is synonymous with the “Ranked and Filed”
- Team Deathmatch
- King of the Hill
- Arms Race
- Completed 50 consecutive waves of Horde mode on every map
There are a total of ten on-disc horde mode maps. This task is synonymous with the "I've Killed Things, Seen Places"
- Get to Re-Up 10
Re-up is the form of prestiging in multiplayer. The maximum level in the game is 100. Once you hit that you have to rinse and repeat nine more times. This task is synonymous with the “Please Sir, Can I Have Some More?”
- Get all Horde classes to Level 10
There are a total of five Horde mode classes. They are engineer, heavy, scout, sniper, and soldier. The most time efficient method for attaining this is completing the first ten waves, then rinsing and repeating. For the sake of not leaving randoms you get matched with high and dry, try finding a group of people to do that method with. This task is synonymous with the “Stay Classy”
- Level any 5 Horde Skills to Level 5
Skills are some of the various cards that you get from purchasable packs. To level up a skill you need to have enough duplicate cards or scrap. Scrap is attained by destroying other cards that you don’t want. The skills don’t have to all be on the same class. This task is synonymous with the “Skills That Make Me a Nightmare”
achievement.*updated the guide with some more info*