I think Christianity is the only religion that teaches love of enemy. Father George Szal tells the story of the painter in a church in China. People kept telling the painter that he mistranslated. Above the door was Love Your Enemies. That couldn't be correct!
Not only is Jesus telling us to love our enemies, He's telling us to be perfect, just as our heavenly Father is perfect.
You would think that it would be easy to love. We were created in love. We were made to love. We love to love.
Concupiscence destroyed our perfect love. But we are free creatures. We are free to choose to love. We can, and should, choose to love. Are we not children of our heavenly Father, for he makes His sun rise on the bad and the good, and causes rain to fall on the just and the unjust? For sure, it is this love that distinguishes us as Christians. This is not a mistranslation, a mistake. It is who we are. We are the children of God, striving to be perfect as our heavenly Father is perfect.