Real Megabuster unlock question

Hi all, just looking for a bit of advice on unlocking the megabuster. I followed the guide on here for the game and something went wonky along the way. I got zombie genocider no problem, after doing case 1-3. when i got to the security room to wait out the time for the helicopter i get a cutscene for case 1-4 and the game basically fails because the next cases start time finished.

my question now is do i need to get the kills for zombie genocider again and keep up with the story so i can get on to the roof or do i just need to complete the game having already got zombie genocider once already? My kill counter has reset back to 0 though I still have all my PP levels and such.

thank you for any help you can offer

RSBennett said:If you already quit out and started a new game, you will need to achieve the ~53k kills again.

After achieving Zombie Genocider (or any achievement in 72 hour mode) you need to finish the game and get an ending/rank (which does NOT require keeping up with the story cases). When the story "fails", there is an option to keep on playing and you need to select that and keep playing until the 72 hours is up and the helicopter arrives.

If you quit out after the story fails, it won't unlock. The game tracks achievements internally - it doesn't just check your actual Xbox Live achievements. If you unlock and achievement and see the in-game display that you got it, then quit and load your save, the game no longer knows you unlocked the achievement and will not give you the reward for it at the end of the playthrough. The same goes for all items unlocked through achievements.

Ah dammit. When the game failed I’m pretty sure it didn’t give me an option to continue though, just to reload my save and stuff. I’m in the middle of getting the kills again now and I’ve already done 1-4 so I’ll be able to go through the security room without triggering anything so it should be clear sailing.

Thank you anyway kind sir!

Best game ever.