Although there are many expectations regarding the way in which the end of the world will come, there are three ways for which many scientist and researchers agree that might happened (some of them also have other demolition events in mind but most of them agree about this three ways). The results of many researches show that these three are most likely to be the one that will be responsible for devastation of our planet and changing our life as we know it. Lets begin with the expectations that Super Volcano Eruptions will burn down many cities and cover with ashes many more and at the same time block sun emission for weeks even months.
The thing very few of us know is that although active volcanoes can be found in only couple of parts of the earth, there are many inactive volcanoes which are going to be reactivated and cause massive devastation. For instance, Yellowstone State Park located in the US is famous for it thermal springs and old geyser activities. This park is sitting on top of the biggest volcano on earth, and researches shows that this "inactive" volcano has a pattern of eruption on approximately every 650,000 years (guess when Yellowstone will come close to 650,000 years since the last eruption). Giving this example you could see what will happen when the inactive volcanoes become active and start erupting.
Another way of destruction is the highly intensive earthquakes, which are a consequence of a sudden discharge of massive energy in the earths' crust resulting in massive seismic waves. These seismic waves will shake the planet earth and will cause gigantic destruction of every object above and below the ground. As this is not enough these intensive earthquakes will cause massive shifts in the earths plates and thus we could be witnessing the disappearance of many mountains and the arising of totally new mountains. The shift in the plates could also cause a tsunami (I don't not want to explain the intensity of the destruction force of the tsunami, because of bed memories and experience).
The third way is major floods as a result of high increase in the water levels. The high increase is consequence of climate changes, thus the ice on the poles is melting and you get the picture. The last one is especially important if you are located by water surface, you should take the precautionary measure to protect yourself.