Let me try an extreme example of how your childhood can affect who you are, but you should still be held accountable for your actions.
There are many examples of murderers from less than ideal backgrounds…charles manson and jeffrey dahmer come to mind… but they should absolutely be held accountable for their actions. No doubt about it.
And yes there are folks from great backgrounds who murder also. Menendez brothers come to mind. But a bad childhood increases the odds of extreme bad behavior.