They are hard questions, you know? I mean, there's an answer, and the answer is true. But for people to believe that answer, they have to believe that God. All the "proof" of why God will not just take away all the bad lies in the bible, but if you don't believe that the bible is true...then you won't believe the answer is true. So the question becomes then, "If someone gives you an answer to your question, but it is an answer that you don't want to believe...could the answer still be true?"
See, here's the thing, God tried this once. God tried to be "all powerful" in the eyes of humanity.
Genesis 6:5-8
"The LORD saw how great man's wickedness on the earth had become, and that every inclination of the thoughts of his heart was only evil all the time. 6 The LORD was grieved that he had made man on the earth, and his heart was filled with pain. 7 So the LORD said, "I will wipe mankind, whom I have created, from the face of the earth—men and animals, and creatures that move along the ground, and birds of the air—for I am grieved that I have made them." 8 But Noah found favor in the eyes of the LORD. "
What I'd like to point out is that people's first reaction of what to do about bad things is exactly God's first reaction. People want to just stop all bad things from happening. So did God. The difference was that God actually had the power to stop all the bad things from happening.
I'd like to point out here a kind of dichotomy. See, in the beginning, right after God creates man and woman, he says that it is good.
Genesis 1:31
"31 God saw all that he had made, and it was very good. And there was evening, and there was morning—the sixth day."
By the time Genesis 6 rolls around, there is both good and bad. I want to be clear here. God made stuff, and stuff is good. The good stuff God made started acting in very bad ways, and their hearts were filled with evil all of the time. So, at the time God decides to take action because of the bad stuff going on, there is also good.
So what am I trying to say? The situation then is no different than the situation now. If God were to act on all that we call "bad" (which we really should make a distinction between bad and evil), not 1 person on this earth would be left. In the bible, Noah is left because it says that Noah "found favor in the eyes of God." This does not mean that Noah was not evil in any way, it just means that God decided to let Noah carry on for people so that God wouldn't be destroying everyone.
And let us be clear. God did this. God, using a flood, destroyed all evil in the world. It was His right to do so. However, along with all the evil in the world, He destroyed so much of the good too. Let's see how God felt after he did this.
Genesis 8:20=22
"20 Then Noah built an altar to the LORD and, taking some of all the clean animals and clean birds, he sacrificed burnt offerings on it. 21 The LORD smelled the pleasing aroma and said in his heart: "Never again will I curse the ground because of man, even though [a] every inclination of his heart is evil from childhood. And never again will I destroy all living creatures, as I have done.
22 "As long as the earth endures,
seedtime and harvest,
cold and heat,
summer and winter,
day and night
will never cease."
There is mention that God feels pain in his heart because of what the people were doing on earth before the flood. Noah offers a sacrifice to God (as is custom in the Old Testament Law). The Lord at the smell of it, which is pleasing (good), makes a statement that He will never again destroy all living creatures.
So, I finish where I began. God already tried to rid the world of all bad. That didn't work, because if there is even 1 person left after He is finished, there will always be bad left. God knew that there would need to be a way to separate the good from the evil in the hearts of people. A way to pay for all the evil in the hearts of people WITHOUT destroying all people. I do not pretend to know all of the mind or thoughts or depth of God, but I would venture a guess that at the point in the story when God decides He will never destroy all living creatures, is also the point when He remembers that there is a plan that will take care of the evil in people's hearts without destroying their hope for a future with God. Jesus Christ is the fulfillment of the plan to reconcile us to God. Jesus is how God decided to pay for the evil that is in all of our hearts.
God won't kill everyone, that is why there is good in the midst of bad in the world. We have this idea that we are entitled something. There is this idea that God owes us something. God does not owe you anything. God created something good in the beginning. If God owed anything to anyone, it was to Himself. See, you and I are living in a period of the grace of God. I believe God hurts, that He feels pain right now at the countless number of things that are going on on earth that are evil. God feels every hurt from evil. But in spite of that evil, there is hope for us. There is hope for "who we are in Christ." That is, hope for us without all the evil that we are living with on this earth. It is because God loves us so much that there is hope for us, and that we are not all already destroyed, because God has every right to destroy us all right now...no hesitation.
If you don't think the bible is true, this answer is hard to accept. Even so, the answer is true. God loves you, He wants you to know that He loves you, and He gave His son to die for you so that you could be presented to Him without all the evil in your heart and spend eternity in worship of the God who is worthy of that worship.