On the polite assumption that that you are interested in an explanation, instead of an argument, here are the facts.
It is true that God is all-powerful [Matthew 19:26]. It is true that God created ALL [Nehemiah 9:6]. It is true that God created whom we now refer to as Lucifer [Ezekiel 28:11-15]. It is true that Lucifer fell from God's grace [Isaiah 14:12-14]. It is true that God knew Lucifer would fall [1 John 3:20]. It is true that most will not enter the Kingdom of Heaven [Matthew 7:14]. It is true that God is all-good [Mark 10:18].
It does not follow, however, that God created evil and is evil. There is no evil that dwells within God; it is contrary to His perfect holy nature [Psalm 5:4]. God is too pure to even look upon evil [Hab. 1:13].
God made the devil - not as the devil, but as Lucifer: the most beautiful, powerful, grand angelic being in Heaven. He was created by God to serve at His throne. The name Lucifer means "morning star." God created Lucifer to serve mankind by bringing light and truth to the world.
Lucifer was created perfect in all his ways, including his free agency, until he considered himself God's peer or better. In his holier-than-thou original pride, Lucifer tried to exalt himself above God, willfully sinning against his Creator. Instead of being the "light bearer," he chose to become "Satan" which means "adversary" – the enemy of God. His self-appointed purpose is to oppose God, to bring confusion and destruction to mankind and to thwart God’s plan.
Yes, God created an angel who was good, knowing that the angel would fall and rebel. From the beginning, God has provided every being with free will - the choice to exchange 'Thy' will for 'my' will. Lucifer and a third of the Heavenly angels chose the latter. Thus the drama began. Lucifer started it; Adam and Eve continued it; you and I inherited it; Jesus Christ cured it; God will finish it.
Remarkably, you and I are active participants receiving an eternal vote. Contemplate the next sentence fully. "If you weren’t permitted to reject God, following Him would hold no meaning."
So what is God's plan? To protect those who vote 'Thy' will from a future tainted by evil. As a result, eternal salvation will be the never-ending continued discovery of God the Father's glory, power, creativity, goodness, and love...by the power of God the Holy Spirit through God the Son Jesus Christ. The Gospel in 10 Words - We’re saved from God by God through God for God.
No, God did not create evil. He created a universal existence giving potential to evil through free choice and rebellion. Lucifer's pride led the way. A hole does not exist until you remove the good soil; evil does not exist until you remove the goodness of God's glory. The Good News is that God provided The Filler on the Cross in order for that Cross-shaped hole in your heart may be filled forever [John 3:16-17].
God created this cosmos to serve as an arena in which evil and suffering can be rooted out, finally and eternally – while simultaneously maintaining the human capacity to exercise free will and, thus, to experience and express love.
I would like to direct your attention one of the most sweeping and most loved promises in all the Bible, Romans 8:28:
"And we know that God causes all things to work together for good to those who love God, to those who are called according to His purpose."
Perhaps more than any other promise in the Bible, this verse has helped people trust God through experiences that seemed utterly pointless and painful and evil. People have held fast to the "all things" and believed the Word of God – this too, this terrible thing, this seemingly pointless thing, will turn out for "my good." God's math.
So no, God is not the author of evil. However, He has ordained to permit evil to occur; it is within His Sovereign will to allow it to exist so that He can eradicate it forever, eternally. There is life after death. We were all created by God as eternal beings. Your eternal forwarding address is willfully determined by 'my' or 'Thy'. Those who choose 'my' in this life will battle evil eternally, absent all God's goodness. Those who choose 'Thy' in this life will rejoice in God's goodness eternally, absent all evil.
Dare I say, God's goodness today is radically undervalued, and evil's eradication tomorrow is way undercontemplated.
So what's the cost of evil?
It cost Jesus everything on the Cross. In Christ, there are no addendums. There was no bailout.
Those who accept His payment in full by freely accepting His Divine mercy - by acknowledging His life, sacrifice, death, burial and resurrection as real - are forgiven. Jesus exchanges all His goodness for all your badness. It's the ultimate unfair trading practice.
But God the Father never said it would be fair...to His Son.
The most important third question ever asked in the history of humanity was by Jesus to His Apostle Peter, "Lovest thou Me?" John 21:15-17 It is the single question we cannot avoid. You cannot avoid.
Christianity is not a hypothesis, it is not a debate, it is a marriage proposal.
My heartfelt prayer? That you willingly choose 'Thy'. That you invite Christ alone to help Himself to your life. That Christ alone becomes your perpetual novelty.
That you say, "Yes, I do!"
Lucifer started it with 'I' calculate;
Adam and Eve bought into the math;
You and I tithe as Narcissistians;
Jesus Christ paid our debts in full;
God will soon close the books.
You do not want to be on the wrong side of the Cross when He does.
If you doubt, don't.
Self-sufficient pride is entirely and eternally overrated.
In Christ – sign me:
Grateful forgiven sinner,
"And you shall seek Me and you shall find Me, if you seek for Me with all
your heart" (Jeremiah 29.13).