Also known as Holocaust 2000 and Rain of fire.
Kirk Douglas decides to build a nuclear power plant next to some sacred caves (as you do.) Which is handy as his son who happens to be the anti christ, is looking for a new hobby and plans to use it to bring about Armageddon.
After pretty much the world and it's dog tries to stop his plans, Kirk finally gets the hint things might not be quite right when he has some badly blue screened dreams in which he experiences terrifying images of the end of the world. And we experience the equally horrific sight of the then 61 year old naked.
Que a father son stand off and Kirk somehow managing to get a woman at least 30 years his junior to sleep with him and this is a fun not quite Omen rip off.
I just found out this was directed by the guy behind OK Connery and The Pumaman...