i dont think anything will kill EVERYONE right away. but imagine...just from the law of probability...here we are living day by day, yet earth is 4 billion years into its cycle...has another 3-4 billion left...it is old. a lot of things have happened to it that we only pretend to know about. day by day we live, in a multibillion year old planet. anything can happen at anytime. yellowstone blows up. meanwhile, 4 cat 5 hurricanes are forming simultaneously in the gulf, off the coast of africa, and in the pacific...and hit north and south america hard. then another earthquake hits eastern asia and the largest tornado outbreak in the history of the world hits the rest of north america. it all hs to happen at some point.....the law of probability demands it. it HAS to especially since we are only 4.6 billion years through our journey. we have been around 4 million years and we think we havr this shit figured out. humans can NOT survive forever. i dont think any species can. but i think the universe works together when it comes to putting conditions together to create life, and it adapts.
It's either gonna be a nuke, disease or supervolcano that takes out the large majority of humans. The thing is, humans are like cockroaches so there are bound to be some that survive.