129. Model of a Modern Major-General. Train all Units, across any number of playthroughs.
Today’s update effectively corrected the problem where this achievement was not fired because of Lancer unit not counted.
To get this one you need to build all units, start with any civilization you like and play through all eras, build all units in each era.
Then start a new game for each other civilization using advance options to start in the era where the special unit is located, for example to create the missing Lancer I created a game in Industrial era to have the unit available right away.