I'll do a quick play-through of a possible scenario, but you'll likely pick this up naturally.
Play a game on Casual, and start in India. Evolve the following, which can be found on the 'Vampires' tab.
Blood Rage
You should already have the DNA you require when you start the game, both to unlock Blood rage and to use it straight away. Simply select it and highlight India, then you'll go into a Blood Rage and infect and kill many in India.
This will pop the achievement.