He told us he will come through the sky the same way he went up he will come back again. To judge the living and the dead.
The dead will rise from the ground and it will be the day the world ends.
But it will only end the way we know it. The good will be with Christ. The evil the ones who reject God will be thrown into the eternal fires of hell.
Remember hell is eternal life without Christ.
It will be a great day indeed. There will never be anymore suffering, death, etc. Basically it will be the earth it should have been and was before the sin of Adam and Eve.
If Adam and Eve would not have sinned there would have been no death, no sin. The world will once again become the garden of eden. Heaven ON Earth.
Maybe somehow through all of our own sins we all will privately learn our lesson.