No I would never kill someone even if I had the chance to do it. These is because I feel that the right for serving justice is not in my hands. Instead, it is the duty of the legal system to carry out whatever form of execution of sentencing that it deems necessary.
In other words, I would not even want to kill my worst enemy and take the tag of the killer with me to the grave. In my view, everyone should avoid taking the law in their own hands and should hence abide by the rules to form a stable society.