Achievements menu bugged?

+1. I have completed Halo 2 Anniversary Solo Legendary, the main menu says I have done 15 chapters on 15, but I have no achievements since it says I failed to get Regret achievement. Just done this chapter again for a second time, but at the end there is
non achievement!!! Fix these bugs!

Hi Ice, my name is Rodrigo. I'm an Independent Advisor and a member of the Microsoft community and I'd love to assist you today.

I am sorry to hear that.

Please, clear the local saved data, power cycle your console, and then launch the game again.

To do it, follow these steps:

Press the Xbox button on your controller to open the guide.

Select Profile & system > Settings > System > Storage.

On the Manage storage devices screen, select: Clear local saved games. This deletes games saved to your hard drive, but they'll still be saved to the cloud.

Then, power cycle the console.

Turn off your console by pressing the Xbox button on the front of the console for about 10 seconds, until it shuts down completely.

Unplug the console's power cable. Wait 60 seconds.

Important Be sure to wait at least 60 seconds. This step resets the power supply.

Plug the console power cable back in.

Press the Xbox button on your console to turn it on.

Finally, launch the game.

Let me know if it works!

Source:

https://support.xbox.com/help/hardware-network/power/restart-or-power-cycle-console

does it completely freeze, like, forever util you turn your xbox off? Is something happening when you wait and do nothing?

Clear your cache and look for corrupt files to see if this helps.

That is a lot of achievements, congrats! But that might be the problem, too much stuff to load, you can try to delete your cache by going to "Settings - Storage - Device options (Y) - Clear system cache".