Here is the full list of all 12 The Pillage achievements.
Collect 50 hearts in game
Get a kill combo of 15 or higher
Kill 500 cops
Have nine hearts at one point in time
Get 500+ kills in a round
Get 750+ kills in a round
Get 1000+ kills in a round. There are no civilians, only cops and gang members now.
Get an APB called on you for killing so many cops.
Kill 30 angels with a one-damage stab
Get 250+ kills in a round
Get an 8x kill combo, putting you into slow motion.
Cause a gang to attack you