The achievement is unlocked when you
reach level 30 during a single playthrough. It is
missable because it is easy to get to the point of no return well before level 30. You may expect to level up once or twice after landing on
Tartarus. However, if you are below level 28 when Tartarus becomes available as a destination, do some leveling before going there and triggering the point of no return.
The achievement becomes much easier to get if one's intent is to play one or both of the DLCs. The base game is capped at level 30. Each of the two DLCs raises the cap by 3 levels. If one is only playing the base game and is playing efficiently--no grinding for the sake of XP--one may reach the point of no return at around level 25 even if all tasks, side quests, faction quests, and companion quests are completed.
Accordingly, if you feel you are not leveling fast enough and are not going to play either DLC, make it a point to earn extra XP by taking every opportunity for a skill check, a lockpick, a hack, and discovering locations—vending machines, workbenches, and named places on the map—to help you level up.
On the other hand, if you plan to play through
Peril on Gorgon for The Outer Worlds and/or
Murder on Eridanos for The Outer Worlds, you can take a much more relaxed approach to this achievement. This is especially the case because either or both of the DLCs can be started from the system save file created upon reaching the point of no return. So, you can play the DLC(s) knowing the precise target you need to attain to put this achievement within reach.