- Estimated achievement difficulty: 3/10 [Achievement Difficulty Rating]
- Offline or Online, Solo or Co-Op: 44 
- Offline or Online, Co-Op Required: 2 
- Approximate amount of time to 1000: 12-16 Hours [Estimated Time to 100%]
- Minimum number of playthroughs needed: 1
- Missable achievements: No
- Does difficulty affect achievements: N/A
- Unobtainable/glitched achievements: No
Step 1: Complete Solo Playthrough
Now, I suggest playing this game solo solely for achievement purposes. The game's achievements are very finnicky when playing co-op, and there is no guarantee what will or won't have issues as far as tracking progress for quests, codex entries, etc. If you DO play in co-op, you should ONLY play in co-op and try to always play with the same person/people so nothing changes as far as the game is concerned - you should probably never swap back and forth between a solo and co-op playthrough either. Playing solo will bypass all that.
Anyway, whichever way you decide to try for the completion, your main focus should be to complete the story first. There is nothing missable, and all content and locations will be available to play after the story is complete.
Step 2: Mop Up Non Co-Op Achievements
After you finish the story, look through your list and see what is left to complete. Finish up any remaining side-quests, find out what if any codex entries you are missing and where to find them, and see if you have any miscellaneous or combat related achievements to knock out and do so now. You should only have two achievements left at this point which will require a quick co-op session.
Step 3: Co-Op Achievements