The Bible mentions Satan and demons, or the fallen ones, but is there different kinds or ranks of demons that exist? Are some demons more powerful than others?
A Fallen Angel
Demons are simply fallen angels that eons ago chose to follow Lucifer in his rebellion. Lucifer (later, Satan and the Devil) tried to usurp the throne of God…to become God actually. Instead, Lucifer was cast out of heaven…and nearly one-third of the angels may have followed his rebellion. The Apostle John wrote about Satan, sometimes referred to him as that old dragon or serpent. This is a clear reference to the fall in the Garden of Eden, but John wrote of Satan that “the great dragon was thrown down, that ancient serpent, who is called the devil and Satan, the deceiver of the whole world—he was thrown down to the earth, and his angels were thrown down with him” (Rev 12:9). At one point in history, Satan and “His tail swept down a third of the stars of heaven and cast them to the earth” (Rev 12:4). When that happened is likely before the fall or perhaps, even before creation of the earth or the universe, so that may be when the seeds of Lucifer’s disobedience took root. You can read more of Satan’s great fall in Isaiah (14:12-15) and Ezekiel (28:12-15). Lucifer, who was created by God to give glory to God at His throne, may have been the greatest of all of God’s creation, not just the greatest of all the angels and demons.
Most believers understand that there’s another world out there. It’s an invisible, spirit-filled world that we can’t see. Therefore, the Apostle Paul warns the church (and us) that “we do not wrestle against flesh and blood, but against the rulers, against the authorities, against the cosmic powers over this present darkness, against the spiritual forces of evil in the heavenly places” (Eph 6:12). And these forces are no weaklings! On one occasion, Daniel the Prophet was praying to God and God heard and answered his prayer, but it took three weeks for the angel of God to reach Daniel with the answer. Why? The angel said it was because “The prince of the kingdom of Persia withstood me twenty-one days, but Michael, the chief prince of the angels, came to help me, for I was left there with the kings of Persia” (Dan 10:13). The angel needed some backup…from a more powerful angel than the prince of Persia, whoever that was. Maybe it was Satan, and Satan was too much for just a regular angel. We cannot know for sure, but we do know the one angel sent from God was no match for the prince of Persia.
There are many different holy angels, like cherubim (Genesis 3:24; Exodus 25:18, 20) and seraphim, which are yet another class of angels. seraphim are only mentioned once in Scripture in Isaiah 6:2-7, but their description is incredible. The seraphim are described as having three pairs of wings. Whether these same kinds of angels fell with Lucifer or not, we just don’t know. I would suspect they didn’t because the seraphim and cherubim served a very specific service for God and may have been unique among God’s creation of angels. Most, if not all of the angels that followed Satan in his rebellion were likely regular angels. Not like Michael the archangel, or Gabriel, the chief messenger for God.
The Victory Over Satan
At the cross, Jesus defeated, once and for all, Satan and his ability to rule the world. Satan’s fate was sealed on the day that Jesus went to the cross. Our Lord said, “Now is the judgment of this world; now will the ruler of this world be cast out” (John 12:31: see also Col 2:15). That doesn’t mean Satan is still not god of this world. The Apostle Paul said that the reason people don’t believe is because “the god of this world has blinded the minds of the unbelievers, to keep them from seeing the light of the gospel of the glory of Christ, who is the image of God” (2 Cor 4:4). It was only because of God’s grace that we were quickened to new life in Christ (Eph 2:1-5, 8-10). All those the Father calls will come to Christ, but it must be through Jesus Christ and Him alone (Jon 6:44; Acts 4:12), but know this; after you’ve trusted in Christ, nothing or no one (Satan included) can separate you from the love or presence of God (Rom 8:38-39).
We cannot know for certain if there are different ranks of demons. I do not believe there is because the Bible gives us no indication of it, but we cannot say for sure. We do know that the demons fall under the rule of Satan and do his bidding, and whatever he bids, cannot be good. That’s okay. God can use evil for good (Gen 50:20; John 3:16), but obviously, we just don’t know what rank of demons followed Lucifer or Satan in the fall. All we know is their time will come (Rev 20). That cannot be changed. Jesus once met a demon possessed man, or should I put that in the plural, because there were actually a “Legion,” for many demons had entered him” (Luke 8:30). This demon was not just one demon, but in fact, a legion of demons, and a legion at that time could be anywhere from around 3,000 to 6,000, so this man was possessed by, not one, not two, or even three demons, but at minimum, a few thousand of them! No wonder his strength was supernatural. Thankfully, if you have trusted in Christ, you need have no fear of Satan or his demons. They might harass you or hit you with spiritual attacks, but we know that He that is in us is greater he who is in the world. Make your calling and election sure, and do it today. In fact, do it right now. Jesus said the gospel includes repentance and faith (Mark 1:15). Don’t let your pride stop you from humbling yourself before God. Remember, pride comes first…then the fall (Prov 16:18).
Here is some related reading for you: Bible Study on Demon’s Names: Verses, Capabilities and More 
Resource – Scripture quotations are from The Holy Bible, English Standard Version® (ESV®), Crossway Bibles. (2007). ESV: Study Bible: English standard version. Wheaton, Ill: Crossway Bibles. Used by permission. All rights reserved.