Re: Whee are the aliens?
Viruses and bacteria trump nukes, asteroids, let alone terrorism.
Unless you're talking viral terrorism.
I think I covered that, with "plague". One of the ancient modes of Armageddon. Biblical, really.
“A life is like a garden. Perfect moments can be had, but not preserved, except in memory. LLAP” — Leonard Nimoy (1931-2015)