Iread multiple times, that this achievements unlocks at the 25th S.T.A.R.S. Labs Catwoman Mission. On my way to the 20 Stars, which are required to unlock the 25th misson i came across the 7th Superman Mission where you need to defend the human. I failed the mission, and right then, the achievement unlocked.
So I guess, this is pretty much random. But due to the fact, that there is a huge amount of people who unlocked it, i guess the best way to get it, is just playing S.T.A.R.S. Labs and hope for the best.