For me personally a tragic backstory or explanation of motivations is a justification, because it is important for me to think about why it is that bad things happen, and how they happen, and if they have any meaning at all, not just for the sake of culpability. I find it reassuring to know that there is evil in this world that comes from a place of experience and reason, however misbegotten. Aimless and senseless evil is what really frightens me.
It is not about 'deserving', it is not about moral transaction, it's not about playing criminal lawyer for my favourite characters - storytelling is not about putting on a performance of virtue kabuki to justify to other people that I promise I'm a good person (which itself is a kind of subterfuge bad people can easily perform! People can lie!) - any beancounter approach to narrative is just miserly and soulless.
Notice that the conversation gets squared down simply to culpability - mostly because it is about personal injury, evil character make me mad and evil character hurt my favourite character - which, if you are not playing along with this pseudojustice, you are basically responsible for the crimes of the fictional character because there is no fictional character to meaningfully hold accountable because they're not fucking real.
And it's completely bizarre when people bring real life justice into this because we find excuses for the things we do in life, even without good reason, all the time. Constantly. This is pretty much the one failure of existence, searching for justification when our justification is poor, that most people struggle with - from little things like not picking up rubbish when we walk past it to big things like not intervening when somebody is doing something wrong and you have the capacity to do so. So forgive me for being interested in people who make mistakes, or do wilful evil, for actual real reasons, let alone tedious, selfish excuses.
Empathy in relation to storytelling is not a crime. It's the point. You're supposed to feel something.