101. Barbarian Warlord. As Bismarck, convert the Barbarians from 10 camps to your side.
For this achievement the 10 camps should be taken/converted in the same game. To get it I setup a huge map, Pangaea with only 1 player and zero city states to let barbarians to have some room to create camps.
Basically I build 3 cities and 3 sets of 2 units searching for camps, it took more than 10 camps as the chances are 50% to get it converted.