Warhammer 40,000: Inquisitor - Martyr

You will get this while going for the 100 Embodied Saint uses. As mentioned in my other guides the starting Sacred Rite was what I had found to be most effective for it. You get 0.01% faith generation per second and it increases by 0.01% for each enemy killed. Just keep at it and you'll unlock the achievement on the way to level 100.