Evil is quite irrational, illogical, and inexplicable . It's so easy to be kind, loving, forgiving, tolerant and caring. It takes energy to be hateful, spiteful, jealous, resentful, and mean-spirited. It takes a lot of energy for us to continually carry our resentments and bitterness toward others, particularly those right in our own homes. At bottom, aside from evils, pain and suffering caused by natural disasters, the evils inflicted by human beings on other human beings is grounded in egotistical lusts for power and control over others.
Pride is the soil in which the seeds of evil are planted.
It is the source of much of our pain. Such a request, however, ought to be given deeper thought. Suppose God did, in fact, rid the world of evildoers. If God were to cleanse the world of sinners I would be erased from existence along with Adolph Hitler. And because we, you and I and a whole lot of others, are a mixture of saint and sinner, angel and beast, the world is consequently a mixture of good and evil.