Marcus, It's Your Father - story Progression in Prologue.
Swimmin' in Glowie Gravy - story Progression in Act I: Chapter 2.
We Struck Gold, Son! - story Progression in Act I: Chapter 3.
My Turf! Cougars Territory! - story Progression in Act I: Chapter 5.
Putting it Scientifically... - story Progression in Act I: Chapter 6.
Okay, Now We Find Hoffman - story Progression in Act II: Chapter 1.
Oh Yeah, It's Pirate Time - story Progression in Act II: Chapter 5.
Thanks for Flying GasBag Airways - story Progression in Act II: Chapter 7.
Anvil Gate's Last Resort - story Progression in Act III: Chapter 1.
Was it Good For You? - story Progression in Act III: Chapter 2.
Lost Your Good Driver Discount - story Progression in Act III: Chapter 3.
Brothers to the End - story Progression in Act III: Chapter 5.
Think You Can Handle That? - story Progression in Act IV: Chapter 3.
Baird's Favorite Kind of Toy - story Progression in Act IV: Chapter 5.
Welcome to -redacted- - story Progression in Act IV: Chapter 6.
Look at That, Instant Summer. - story Progression in Act V: Chapter 2.
OK. Faith. Yeah. Got It. - story Progression in Act V: Chapter 5.
You're Dead! Now Stay Dead! - story Progression in Act V: Chapter 6.
Respect for the Dead - during Act IV: chapter 1, don't cause the destruction of any of the Ash people. it is ok if the computer or the Ash Man does it but don't cause it yourself through collision of gun fire. When you get into Gryffin's Tower but before meeting him, you will walk down a hallway and see an arsenal to your right behind a gate. Approach the gate and when they open, this achievement will pop.
Collector - recover 5 collectibles - I didn't put a separate section in for this but they are all covered in the main guide section. Find the collectibles section from the Main Menu --> Stats & Awards --> Collectibles. From here you can find which collectibles you are missing, including COG tags. Find which chapters you are missing collectibles from and play that chapter over using my guide to find them.
Pack Rat - recover 20 collectibles - I didn't put a separate section in for this but they are all covered in the main guide section. Find the collectibles section from the Main Menu --> Stats & Awards --> Collectibles. From here you can find which collectibles you are missing, including COG tags. Find which chapters you are missing collectibles from and play that chapter over using my guide to find them.
Hoarder - recover all 42 collectibles - I didn't put a separate section in for this but they are all covered in the main guide section. Find the collectibles section from the Main Menu --> Stats & Awards --> Collectibles. From here you can find which collectibles you are missing, including COG tags. Find which chapters you are missing collectibles from and play that chapter over using my guide to find them.
Remember the Fallen - recover all 15 COG tags - I didn't put a separate section in for this but they are all covered in the main guide section. Find the collectibles section from the Main Menu --> Stats & Awards --> Collectibles. From here you can find which collectibles you are missing, including COG tags. Find which chapters you are missing COG Tags from and play that chapter over using my guide to find them.
Ready for More - complete all campaign Acts on Casual or Normal Difficulty.
Ain't My First Rodeo - completed all campaign Acts on Hardcore Difficulty. It may be easier to do this with friends rather than the AI.
That's Just Crazy - completed all campaign Acts on Insane Difficulty. To unlock insane, you have to beat the campaign on any difficulty. I highly recommend playing through this with friends to make it easier.
My Fellow Gears - complete all Acts in Co-op on any difficulty - You have to finish every chapter in the game playing with another player or with two controllers. This doesn't have to be done in one sitting.
We Few, We Happy Few... - complete all Acts in 4 player Co-op on any difficulty - You must complete every chapter with 3 other players. This doesn't need to be done all at once so you can just keep trying through online matchmaking if you need to. However, if you are going for Seriously 3.0, playing through on Arcade Insane with four players will save you a lot of time.