No, the world isn't getting any better, in spite of the many advances we've made in areas like science and technology. Historians agree that the last century was the bloodiest on record (with two world wars, numerous lesser wars, the Holocaust, and so forth) -- and this century promises to be even worse.
And you're right: Behind the horrors that grab our headlines almost every day is the evil, malevolent power of Satan. There is much we don't understand about him -- but the Bible assures us that he is not only real, but also that he is at work behind the scenes to bring chaos and death to our world. The Bible calls him "the spirit who is now at work in those who are disobedient" (Ephesians 2:2). Jesus labeled him "a murderer from the beginning" (John 8:44).
Will the devil ever be defeated? Yes -- absolutely! Some day, the ongoing conflict between God and Satan will be over -- and Satan will be defeated forever. Christ will emerge as the victor, and Satan and his servants will be "thrown into the lake of burning sulfur.... for ever and ever" (Revelation 20:10).
But listen: Satan is already a defeated foe, and his final doom is already certain. The reason is because by His death and resurrection Jesus Christ overcame the powers of sin and death and Hell and Satan. On whose side are you? Make certain of your salvation by giving your life to Jesus Christ today.