The fifth angel poured out his bowl on the throne of the beast, and its kingdom was plunged into darkness. People gnawed their tongues in agony and cursed the God of heaven because of their pains and their sores, but they refused to repent of what they had done.
Revelation 16:10-11//

God offers sinners the chance to repent to the very end – and to the very end, despite Him having revealed Himself, they refuse. While it seems impossible, I need to remember that there are some people so sinful that they would rather spend eternity in Hell than to serve our loving Father.