Throughout the game you will be presented with choices during a cut-scene to do something with evil Karma or good Karma. This is the third choice you will have to make. Choose the
Evil Karma (red) option and complete the red Star mission
Hunting the Hunters to get this trophy.
If you want to know what the choice is, hit the spoiler below:
*** Spoiler - click to reveal ***After battling the angel "He Who Dwells" and getting Eugene's power, you will you will have to convince your brother to not take Eugene in to lock him up. You will then have the Karma options to Redeem Eugene, or Corrupt Eugene. Either way your brother will let Eugene go, but if you choose Corrupt Eugene then you will start to go down the path where Eugene will want to kill all the bullies (Akuran gang members). The Red Star mission Hunting the Hunters is available once the cut scene is over. To beat the mission easily, go to each location that Eugene sends you to and just unload everything you have and kill everyone and everything. After a few locations the mission will be complete and the trophy will pop.