This achievement is self-explanatory.
Also FYI - I went into the last mission on Tartarus with only a few thousand XP in to level 28. I was able to gain two full levels in the final mission.
I’m mentioning this because the game ends immediately following the final mission. I was worried that I would not hit it and that I would have to reload an old save and do some side missions instead. I’m not exactly sure how much XP exactly the final mission yields, but again it was enough to level me from 28 to 30.