Wikipedia's a great place to start your descent into the black hole of doomsday cults, but because a lot of the information is crowdsourced, it should be taken with a grain of salt.
This UFO cult was founded in 1955 by Hon-Ming Chen, who believed that the Earth had gone through five tribulations since the age of the dinosaurs. Supposedly, each time, God came to North America to save its inhabitants by way of spaceship. Chen Tao ended up moving to Garland, Texas, because it sounded like "God's Land," and predicted that on March 31, 1998, God would appear in Chen's likeness on Channel 18 of every television set in North America. Chen offered to be stoned or crucified for his miscommunication with the powers that be, but ultimately the group fell apart, with its remaining members relocating to Lockport, New York. They predicted an additional end of days by the close of 1999 — complete with God ships and nuclear warfare — but later revised their statement. They've been pretty quiet since, which I guess is as happy an ending as one could hope for in a situation like this.
Founded by Marshall Applewhite and Bonnie Nettles in 1974, this group would become known for its mass suicide in 1997. While others were preparing to watch the Comet Hale-Bopp travel the sky, Applewhite and 38 other members killed themselves in matching black shirts, sweatpants, and athletic shoes. They believed a spaceship traveling behind Comet Hale-Bopp would collect their souls and transport them to a higher plane of existence, and had prepared by mixing phenobarbital with apple sauce and vodka. They also induced asphyxiation by tying bags over their heads. It seemed that members died in three groups, each cleaning up after the other, which seems exceptionally morbid if you aren't a person who believes your soul is ascending to a spaceship.
5. Dami Mission
Dami Mission was founded by Lee Jang Rim, who believed that the end of the world would occur on Oct. 28, 1992. He predicted that 144,000 followers would ascend to heaven, while everyone else left on Earth would suffer seven years of war and famine, resulting in the extermination of pretty much everyone and paving the way for the second coming of Christ. This prediction caused a number of people throughout South Korea to panic. On Oct. 28, many a shenanigan went down, including members dressed in white burning furniture outside a Dami Mission church, gathering outside Lee's prison (Did I mention he was arrested for fraud and illegal possession of American currency?), and leaving massive amounts of cash for those expected to remain behind. When nothing happened, the movement dissolved and Lee spent two years locked away.
Concerned Christians was a group initially created to combat New Age beliefs in the 1980s, but things went horribly awry. The group began ascribing religious meaning to many political events. For example, they believed that the president of the United States was the Antichrist (*insert emojis here*) and that the dissolution of the Soviet Union signaled "the time of the end." The group's founder, Monte Kim Miller — a former Procter & Gamble executive — predicted a disastrous earthquake in Denver. It never actually happened, but many members fled Denver, with some relocating to Israel. The group was ultimately ejected from Israel after being suspected of planning to destroy holy cites to bring about the second coming of Christ. Good intentions and all that.
The Brethren are a strict religious group who believe we are at the end of times, and therefore shouldn't have anything, ever. New members give everything away to purify themselves for Jesus' return. Marriage is discouraged, as "the hour is too late." Singing and dancing are only reserved for the return of Jesus, who is still keeping them waiting. During the 1970s, stories started to leak nationwide about The Brethren's activities, so members now keep their locations a secret and are not allowed to speak to family. Relatives of cult members insist that members are moved about to keep from establishing contact. Thus far, the end of days predictions seem pretty chill, but the mass separation from families thing is less so.
Eastern Lightning is a cool name for a doomsday cult, but they also get up to some pretty scary stuff. The Chinese-based group believes that a woman will be the second Christ, born to judge mankind and battle Satan. They've been known to retaliate against members who express a desire to leave by maiming or killing their younger relatives. In one case, they even murdered a young boy. The group ushered in a bunch of chaos by predicting the end of times on Dec. 21, 2012, while the film 2012 was already capturing the nation's imagination. Arks were even sold to survive the coming apocalypse. Very enterprising, at least.
10. Happy Science
11. House of Yahweh
The House of Yahweh has been predicting the end of the world for some time now. The cult believes that we are in a world currently ruled by Satan (a "she" in this case) and that the world will soon experience the great tribulation. They first predicted that four-fifths of the world's population would be eliminated between 1999 and 2002. The claims got weirder from there, with their leader first saying nuclear war would end life on earth in September 2006...only to recant and say that our nuclear apocalypse would instead follow the cycle of a woman giving birth, and that we should expect said nuclear baby sometime in or before June 2007. Now, the group claims that nuclear warfare did start in September 2006 — we just haven't noticed it yet. Good save.
This New Age religious group, founded by Elizabeth Claire Prophet, garnered a bunch of attention in the 1980s when it predicted nuclear warfare. Several members went into debt building fallout shelters and stocking up on supplies. Around this time, Prophet's husband and others were found stockpiling weapons they had bought using false names, leading to the arrest and detention of several members. Ironically, the buying of guns was legal, but they had used false names in an attempt to deflect further criticism of the Church. (Because, oh yeah, they had previously been accused of using sleep deprivation to control its members.) Prophet put a great twist on her failed prophecy, though: She simply told her congregation that they had successfully prayed away the end of days.