I am against Death Penalty no matter how much sins the criminal has because killing for the sake of satisfying your own taste for revenge is fruitless and foolish in the end + it will only make you a more horrible person than he/she is because you cannot find it in your heart to forgive. Another reason will be, if you really are ANGRY or DETERMINED to punish the criminal, then letting him/her die will make the criminal's punishment easy (especially nowadays criminals sentenced to death are killed through lethal injection of some sort or any PAINLESS method). You should at least make him/her realize about what he/she by making him/her live a miserable life or a painful one. That way, your hands are clean legally, you can "enjoy" viewing his/her miserable life in jail + you will have the chance to ponder over things. So, those are my opinions both from my good side and evil side