This achievement speaks for itself really, complete all other achievements within the game and it will unlock when you go back to the main menu.
(Well that's what happened to me when I left Master of Chaos till last and I finished my last map and was still in the map selection screen, I had to go back to the main menu for it to unlock).
For the people that intend to complete the game they will most likely be left with quite a couple of achievements still to get if you haven't done any grinding at all after doing the majority of Story Mode and Ambition Mode.
These will be:
Each of these achievements that has been listed has there own little time consuming or difficulty set method in order to do them, there are great guides already for these achievements so check them out if you need help.
I should also mention you
can now get this achievement since the v1.3 patch, although it wasn't listed as a patch, it is now obtainable.I think that covers everything, if anyone has any suggestions to make this solution better, see's any errors or has any issues with the solution please leave a comment and I will edit it.
Good Luck and Happy Hunting [: