The only thing that can save this civilisation is the apocalypse. Where a small majority of the whole population survive a global catastrophe. The survivors would be the ones to build a new world order, learning from history not to repeat the same mistakes. This can be achieved in various ways, be it natural or artificial causes.
1. Lighting a fuse on Yellowstone
Once a super volcano erupts, it will send enough ash into the atmosphere to block out the sun for months/years ultimately affecting fauna food chain and flora world wide, causing global famine and the death of billions. All you need to do is somehow set off an artificial earthquake with the magnitude of 7+ on the Richter scale and the volcano will go pop.
https://www.youtube.com/watch?v=UPwSN9gUG5c
2. Cool off Gulf Stream
This might be the slowest way to achieve apocalypse. By cooling the Gulf Stream all the coastline areas of the world would face a miniature ice age, especially Europe and North America coast lines. Artificial ice age would devastate fauna food chain and flora in those regions resulting in massive famine half-across the globe.
3. Destroying the food chain
Take good example from Mao, who starved 50 million of his own people due to stupidity. All you need to do is kill all the birds in one area to induce worm growth and all the crops will wither causing devastating famine and widespread cannibalism, and death.
4. False Flag
Take a good example from WW1 and how it started. Today, you would need to kill an important person loved by the people while diverting the blame on some country. Nuclear war would certainly devastate the whole world population, if not even destroy all of it.
5. Russian Hackers
If someone could somehow hack into military infrastructure and get control over the nuclear arsenal, then it's GG.
6. Ebola 2.0
By artificially modifying viruses to cause maximum damage and maximum spread, one could easily wipe out the populations of ANY country.
Just do it, be a hero.