Yes, God can "just kill Satan once and for all." However, God's plan is not to destroy Satan, but allow him to be tormented for eternity because of his undescribable wicked deeds. God banishes Satan to the fiery place of eternal torment (i.e., hell); whereupon, those who reject Jesus' offer of salvation and are unrepentant for their sins go as well. Here are some biblical scriptures, which discuss Satan's utter demise and destruction: 2 Peter 2:4-5: "For if God spared not the angels that sinned, but cast them down to hell, and delivered them into chains of darkness, to be reserved unto judgment; And spared not the old world, but saved Noah the eighth person, a preacher of righteousness, bringing in the flood upon the world of the ungodly..." Mark 9:46: "Where their worm dieth not, and the fire is not quenched." Matthe 8:12: "But the children of the kingdom shall be cast out into outer darkness: there shall be weeping and gnashing of teeth." Isaiah 66:24 "And they shall go forth, and look upon the carcases of the men that have transgressed against me: for their worm shall not die, neither shall their fire be quenched; and they shall be an abhorring unto all flesh." Daniel 12:2 "And many of them that sleep in the dust of the earth shall awake, some to everlasting life, and some to shame and everlasting contempt." Luke 12:5: "But I will forewarn you whom ye shall fear: Fear him, which after he hath killed hath power to cast into hell; yea, I say unto you, Fear him." Revelation 19:20: "And the beast was taken, and with him the false prophet that wrought miracles before him, with which he deceived them that had received the mark of the beast, and them that worshipped his image. These both were cast alive into a lake of fire burning with brimstone" (King James Version Holy Bible). Source: <http://www.Biblegateway.com> I hoipe this helps to answer your question!

One cannot "kill" a fictional character.

well since neither are real...who really cares

God, being all-knowing, knew what would happen if he created the angels destined to fall. He knew what he would do to them as a result, so he created them knowing that they would fall: he could have created them differently so that they would not fall---He's omnipotent remember---but he chose to create those predestined to fall, and then, despite the fact that he was to blame for creating them the way they were created, he blamed them, and consigned them to terrible punishment. The phrase 'mad sadist' comes to mind.