Mighty.Sun.Tzu
The elimination of envy and greed would be a good start, but you would still have anger, rage, hatred, unforgiveness, bitterness, resentment, addictions,
etc creating big problems.
There are two things that if gone from earth there would be peace on earth... in fact, it would be like heaven on earth... and these two things are demons and flesh, flesh being the non-spirit part of a person, the part of a person that will never make it into heaven and demons of course being the spiritual entities that influence bad behavior of all kinds, tempting, oppressing and sometimes even possessing people.
Even if demons and flesh were not gone from the earth, it is possible for a person to have peace within Himself with these two things no longer in control and if you would wish instant and free miraculous breakthrough with this, please feel free to contact me in my inbox.