There was a thin line between mercy and villainy. With one being the product of weakness and the other the product of greed, both were often interconnected. It was only by mercy that you were alive, and such a gesture did nothing to spark any grateful flame in you, only a twisting pit of desire to eradicate such vile beings from the word - even if in the end that would include yourself. Killing was not difficult, it was simply a matter of weighing the blood on one's hands. They said that if you murder a murderer, the number of murderers stayed the same, but they had nothing to say about purging Gotham of almost all of the filthy grime. . This sentiment remained long after you first encountered Bruce, no matter how much he would attempt to deter you from the bloodstained path. Of course, he didn't know why you had began on this path in the first place, but he was determined to stop you from amorality and, frankly, yourself.