I finally got this achievement, after coming back to this forum every now and then to check if this achievement got patched or not. I'm going to relate my story about this achievement now that I have it, to help others still confused about it.
1. The achievement is finally patched and completely obtainable.
2. You must pick up every instance of health vial, armor, and power-up, which includes: Health Vial, Big Keg O Health, Jump Boots, Armor Vest, Thigh Pads, Helmet, Shield Belt, U Damage, Berserk, Invisibility, and Invulnerability.
3. You must pick all of these things up in 1 run of the map.
4. You must do all maps (INCLUDING THEIR NECRIS VERSIONS) but not "Short", "Classic", "Double Prime", "Free Mine", or "Two Fronts" versions.
5. All maps includes all "Deathmatch", "Capture The Flag", "Vehicle CTF", and "Warfare". "Team Deathmatch" and "Duel" are completed within "Deathmatch".
6. Redeemers, +25 Health Packs, Ammo, Weapons, and "Mines/Misc Weapons" are NOT necessary.
7. This can be done in Instant Action.
8. Once the white banner saying "All powerups found!" pops up on the bottom middle of your screen, you are done that map. You can also double check this by starting a game, pressing the start button, and going to the "Game" tab using RB or LB buttons. Use this feature to check the alternate versions (like "Short", etc) of the original maps to make 100% sure you are done the alternates after completing the original map.
9. If you dont get a banner on the bottom middle of your screen when you collect everything needed, you probably already got everything in one run of the map before the patch, and the messege will be in your "Game" tab of the start menu. This happened to me on Arsenal, I know.
10. You do not need another bot, 2nd player, split screen, system link, or a 2nd controller in the game to get this achievement.
11. You do not need to finish the map, just quit out once you recieve the white banner.
Simply get a list of the Vials, power-ups, and armor off this forum. Then do every map starting with Arsenal in Deathmatch to Torlan Necris in Warfare. Get the white banner to appear and quit out or make sure you have that messege in the bottom left of your "Game" tab in your start menu.
Hope this clears a lot up, or at least combines the info and questions out there to a more concentrated place. This is my experience with the game, should all be correct, sorry if you are still having problems and this doesn't help. I'm going to post this in a few threads to get people to see this if they need help.
Achievement Unlocked, February 6th.
100% Retail (1k+DLC): 18Retail 1k Only: 2
100% Arcade (200+DLC): 13Arcade 200: 1
Working On: GH:SH, GH:M, GoW 2, Arcade Discs