One of my closest friends told me that Satan can be redeemed and still have some good inside him even though he's pure evil. I had some conflicts because of her explanation and I wanted to be sure: is this true?
There is no possibility of redemption for Satan and all the evil angels. Jude 6 explains: “And the angels who did not keep their positions of authority but abandoned their proper dwelling—these he has kept in darkness, bound with everlasting chains for judgment on the great Day.”
Revelation 20:10 describes that judgment: “And the devil, who deceived them, was thrown into the lake of burning sulfur, where the beast and the false prophet had been thrown. They will be tormented day and night for ever and ever.” Jesus also spoke of that judgment in Matthew 25:41.