Employee Of The Month Achievement

There are 100 Abstergo challenges in the game, but you only need to complete 25 for this achievement. To view challenges, access the menu and scroll down to "Abstergo challenges". The central display will tell you how many you have completed. Press and on the left the challenges are sorted into categories such as Explorer and Hunter and Simulation. Playing through the story mode and exploring a bit, along with maxing out Kenway's Fleet, should result in completing 60-70 challenges without particularly trying.