Black Ops 3, the achievement “The Ultimate Sacrifice” isn’t appearing. What do I do?

Thanks for that advice, but unfortunately it didn’t work. Is there anything else I can do? Or is it one of those things where no matter what I do, it might pop up in 72 hours?

If that did not work then yes. Sometimes achievements can be delayed and pop up within 72 hrs as you say

Hi,Joseph! I'm Luis, a fellow Xbox Gamer . Thanks for reaching us out here.

Let´s try deleting the account´s cache Joseph

Delete account Cache

Remove Account:

1. Press the Xbox button.

2. Select System > Settings > Account > Remove accounts.

3. Select the account that you want to remove, and then Remove.

4. Close.

Power Cycle:

1. Turn off your console by holding the Xbox button on the front of the console for approximately 10 seconds. The console will turn off.

2. Wait for 5 minutes and then turn your console back on by pressing the Xbox button on the console or the Xbox button on your controller.

Add Account:

1. Press the Xbox button.

2. Select your gamerpic in the upper-left corner of the screen, move all the way down and select Add new.

3. Enter the Email Address and the Password.

4. Read the Microsoft Service Agreement and Privacy Statement, and then select I Accept.

5. Follow the steps to configure your Sign-In & Security preferences to add your Microsoft account to your Xbox console again.

After that, try to play the games again.

Some thing has happened to my black ops 3 I don't no what to do

Probably the hardest i’ve completed from is two birds for 2019 Modern Warfare, it isn’t that difficult but soon im going to get the easter egg endings in black ops 4 zombies because they give you achievements. : )