Either nuclear weapons, or terrorists.
Maybe something like 'the Avengers' can happen. Who knows!
Greed - the desire for money, power or both
Animals would be so freakin tired of all the stupid people destroying the nature.. Owls will attack you from above and so
Someone saying to another person "Oi, wot u staring at?!!"
Greed, like all wars.
But it won't happen,
Honesty and clear thinking. Honestly and clearly, we do not belong here. This planet is so well balanced. A piece of art. What are we doing here?
The spread of Islam
The fact that the ban on Russian child adoption in the US came too late
Stupidity, like the last two.