It would be ridiculous to think that any human being, or even all of humanity collectively, could somehow manage to successfully destroy the world, if by "the world", you are in fact referring to the planet upon which we live, the galaxy and universe to which it belongs, or to a fictional planet, galaxy...
Best answer: It would be ridiculous to think that any human being, or even all of humanity collectively, could somehow manage to successfully destroy the world, if by "the world", you are in fact referring to the planet upon which we live, the galaxy and universe to which it belongs, or to a fictional planet, galaxy or universe that exists within the reality of the story you plan to tell.
For even if humanity itself were to disappear from this Earth, the Earth itself would remain for quite some time. To completely expunge all life from this planet would not erase the planet itself, and although semantically the world would not technically be "destroyed", if we weren't around anymore, it wouldn't make much difference if there was nothing alive here to be able to appreciate it anyway.
Even unleashing the most powerful and dangerous technology that we have at our disposal could not guarantee the obliteration and erasure of life on this planet. Even with tens of thousands of atomic, nuclear, hydrogen and neutron bombs detonating in a short span of time, there's little proof that such a calamity would be enough to extirpate each and every species alive today.
That being said, alien civilisations - especially those capable of traversing the incalculable distances between worlds across the vastness of space, would obviously be privy to technologies which we could not even begin to conceive or comprehend. Scientists don't even classify Humanity as a "Type 1" civilisation. The inhabitants of this planet have only been piloting heavier than air craft for a little over a century and we've only managed to break the pull of Earth's gravity to send objects into space for less than 70 years.
Alien civilisations which are able to harness all of the energy in their star system would possess a level of technology that we simply could not envision, much less fathom. It would be akin to attempting to explain the intricacies of a nuclear reactor to a Horseshoe Crab to think that we could wrap our heads around what beings like that might be capable of doing.
However, if your goal is to devise a way for a group of people (or whatever else you might like to call them), to kill every living thing on this planet or another, or at least the intelligent life forms, you would have to focus on targeting the most basic necessities and conditions that need to be met for survival.
Having read many, many, many books and stories that deal with such things, I can tell you that Cormac McCarthy's "The Road" paints the most convincing, realistic, believable and frightening scenario that I've come across thus far. Without access to sustenance, people die. If there's no food and no water, there's no life. Likewise, if it's too hot or too cold, people cannot survive. If a disease, virus, germ or some other agent were to be released - one which human beings were unable to fight off, that would be the end of us. Lastly, we are the dominant species on this planet. If that were to change, either because we were to foolishly modify an existing species or to create a new one, or if an alien race were to arrive here with the goal of exterminating us, that would be the end.
Nearly all works of fiction that deal with the obliteration and erasure of mankind follow one of those methods.
Of course, the most common is an act of God, some natural cataclysm that snuffs us out, but as you're asking about an intentional act, super-volcanoes and pole shifts and magnetic fields and gamma rays and the swelling or ebbing, the approach or the retreat of the sun, the impact of an asteroid, meteor or comet, all of those things happen by themselves. But there have been instances of alien species causing such things, notably the "Bugs" of Klendathu in Heinlein's book and the "Fithp" of "Footfall", both of whom were capable of harnessing asteroids to direct them on a determinate course to be used as a destructive weapon.
2 weeks ago