A DwaparaYuga Avatar
During the last DwaparaYuga, which was predominantly an age of Rajas (passion/power) the earth was filled with Rajasic people and there was chaos and war everywhere. Fight for power was destroying the earth. On the plea of mother earth Lord Vishnu incarnated as Lord Krishna and killed many demons and evil kings.
His mission was not only to destroy the evil but also to give the pious people with true Dharma so that the true spirituality is understood by the people of the age.