Is slaughtering one's enemies clearly rotten spiritual fruit ? .... Would Jesus kill a heretic?

If Jesus said in Matthew 5 that even holding a grudge is equivalent to murder, then murdering many times is not any sign of spiritual fruit. Jesus never advocated murder. Unfortunately, humans throughout history have twisted the scriptures to make them fit their agendas it's called "verse jacking" or "proof testing". This is why the word of God has been compared to being sharper than a sword. If you don't know what you're doing, you will hurt yourself and others around you for wielding it improperly. If you have a malicious agenda, you can use parts of the scripture as a weapon (manifest destiny, spanish inquisition, etc.), but that never means you are a follower of Jesus Christ.