Much has been done in the guise of Christian faith that has discredited rather than brought value to the teachings of Jesus. Christians like other religious adherents fall prey to vanity and exclusive tendencies that work their way out in anger and persecution and mimic the very opposite of what we would call peace on earth.
The fundamentalists among us Christian's love to highlight the wrongs of others, the judgment due to others and brandish the verses in scriptures that herald Jesus as being the only way to salvation. If their attitude is anything to go by I don’t know if the world needs to be saved into a place that replicates this pride and arrogance. It is a future I certainly don’t want to be a part of.
If one has to focus on fundamentals the part of Christian faith I would rather be fundamental about is the fact that we are ‘all’ made in the image of God and we all are as much ‘good’ as we are ‘bad'. What is distinct about the Christian is that they recognize the darkness within them that needs redemption and their identity is not determined by how good they are. This ought to keep the Christian humble and non-judgmental of others. The other fundamental I would be fundamental about is that we are called by Jesus to love and pray for our enemies. If we are living by this creed we have to drop our weaponry of words and sharp judgment and reach out ways that transcend the obvious. Maybe in these ways we can say that Christianity will bring peace to earth. (This has been inspired by Tim Keller’s thinking in the book ‘The Reason for God’.)