I had these achievements all glitched out and would NOT pop. I tried them all multiple times, tried new save files, tried offline vs online, waited weeks for it to pop, and got nothing. The solution below is what I found on some forum, and it worked!
Glitched Achievements: One Way To Do It, Henny Penny, Abandon All Hope, Legendary Gunsmith, An Ocean in Storm.
MAKE SURE YOU ARE USING THIS AS A LAST RESORT.
Delete everything. Uninstall the game. Delete Save Data. Delete Reserved Save Data.
You need to make sure every trace of Rise of the Tomb Raider and all save data is gone. Restart your Xbox. Reinstall everything and go get those last few achievements!
Good Luck and Happy Hunting.
P.S. I appreciate any and all feedback.