“Now since the children have flesh and blood in common, Jesus also shared in these, so that through His death He might destroy the one holding the power of death — that is, the Devil — and free those who were held in slavery all their lives by the fear of death.” Hebrews 2:14-15 HCSB

The Devil lost his power over death when Jesus took away the keys of death and hell.

“and the Living One. I was dead, but look — I am alive forever and ever, and I hold the keys of death and Hades.”

Revelation 1:18 HCSB

https://www.bible.com/72/rev.1.18.hcsb

The devil no longer has the power over when we die. Jesus does. The devil never really had the power because He could not kill those who God would not allow. But now we have power over during death we don't need to be afraid. It is a step in the right direction, toward heaven. Unless you are not where you need to be with God. Then death should scare you a lot because then you are one step closer toward Hell. Since God gives us a choice, heaven or Hell, he does not send anyone to hell they choose it themselves. The way to heaven is to line up with Jesus and His word. The way to Hell is to reject Jesus. It's up to you and me. Jesus paid the price to get us there. It is up to us to accept the free gift of salvation on God’s terms. We cannot accept salvation but change all the rules. It is God’s way or the highway to Hell. 

The devil has been defeated. He no longer has the power over our lives that we allow Him. He is after all just a fallen angel and not God. He was created by God. But the lust of power turned His heart away from God and toward getting God off His throne. Which he never accomplished. He was cast down from heaven along with his loyal angels. 

With God on our side, the devil is at the disadvantage. Without God, we are at the disadvantage. We are made lower than the angels as humans, but when we step on the other side to eternity we will become higher than the angels alongside Jesus. The devil has been defeated, stop giving him back the power that was taken away from him and walk in the power God gives you.