Praying for the death of your enemies runs contrary to the gospel of the Kingdom of God. Our Heavenly Father desires that all men and women should come to repentance, embrace His salvation and come to the knowledge of truth. Jesus made this very clear in his earth life and teachings. Also let's not forget that God prepares a table before us IN THE PRESENCE OF our enemies - in their presence NOT in their absence.
And why do you think it's done in their presence? The answer is simple: to give them another opportunity to see the goodness of God and open their hearts to embrace salvation and love.
We may pray for the destruction, the termination, the thwarting, the nullification and the annihilation of the schemes, strategies, plans and works of our enemies but not for the death of the individuals themselves. Whether a man dies or lives is outside our jurisdiction. That must be left for God to deal with. He is the ultimate Judge. That's His call not ours.