Legacy's End achievement in Starfield
1. Probably a good idea to make a hard save (vs autosave) after each quest (I made some mistakes, see below, and had to restart several quests earlier).
2. I have been doing all sorts of questlines randomly. The quest The best there is actually disappears for me when I was doing other things. I knew that I had to talk to Jazz and Navea on the Key, so went there and the quest started even though it was missing in my inventory..
3. I think you have only 1 chance if you screw up on stealth missions. In the best there is, I forgot to actually wear the uniform you steal. While I was talking to Huan via intercom, my wife Sarah started attacking the guards. I figured not my fault, completed the mission and Ikande chews me out at the end of the mission. I figure no big deal.
4. In the mission Absolute Power I started the stealth part at the end, and again Sarah does her own thing and starts a firefight. Again I figured no big deal. This time at mission end, Ikande gets really mad, throws me in jail, the UC is now my enemy, and the Crimson faction questline is comepletely removed. Thus, this achievement can be missable. Because I forgot to make some hard saves, I had to restart all the way back from breaking the bank, as that was the last one I did. Annoying, because I had to recollect the files for Burden of Proof.
5. With regards to Burden of Proof, there are 20 files to collect, but you only need 16 to get the Legendary Pistol Memento Morii. I got it before I started Absolte power (because I had collected all the other ones prior). There is no addition rewards apart from the little credits she gives for each file you give her. Personally this weapon is really good (I specialized in pistols as well).
6. I did not have the glitch on the Legacy, but most people mention making a hard save before the last part where you have to download the credits. Thus after hearing the recording (you need to, to get the quest to continue), make a save. Also, do not forget to pick up the Legendary Rifle The Revenat next to Kryx. This rifle is OP.
7. I had no issues with the last battle, but I had done the mission Overdesigned prior. Make sure you do the mission correctly and get the Kepler R, as it a much better ship than the Kepler S. I did not even upgrade my ship, and easily destroyed the Crimson fleet. It is a class C ship, so you would need to max out piloting (can easily be done by repeatedly doing the pilot simulator).