There's also the Hitler Paradox. A high-tech thinktank develops time travel. They try to kill Hitler.
Paradox 1) Killing Hitler at any meaningful point in the timeline prevents World War 2. Doing so removes the postwar Military Industrial Complex that never gets created. This prevents the accelerated postwar technological development that leads to the thinktank being created in the first place and the technology to build timetravel technology.
Paradox 2) So many people will be trying to kill or protect Hitler that they will cancel each other out. Eventually the factions will try to destroy timetravel before it is developed to end the conflict on their terms. Also known as the Rick & Morty paradox, from the episode Rattlestar Ricklactica .
Paradox 3) There are two time-traveling factions: the "Snakes" (symbol is an upright arrow or an oroboros), who want to preserve the "true" historical timeline, and the "Spiders" (symbol is an eight-pointed Chaos Cross or a spiderweb), who want to disrupt the timeline. The latter either wants to impose their moral and political beliefs on the space-time continuum and right perceived wrongs or nihilistically disrupt the timeline for their amusement. Either the Snakes want to protect Hitler and the Spiders want to kill Hitler or the Snakes support and foster the Allies and the Spiders support Hitler's rise to power and the creation of the Axis to trigger a world war. Hitler would never have been important without the events of the Time War. See Fritz Leiber's Change War series or Kurt Vonnegut's Mother Night .
Paradox 4) Adolph Hitler becomes a paranoid with a strong persecution complex because random people keep trying to kill him throughout his life. He creates a group of loyal followers to protect him that leads to the creation of an autocratic police state with him in the center. The perceived enemies are Jews and people with Left Wing politics because those are the two biggest Venn Diagram circles among his would-be assasins. Israeli and Soviet time-traveling hit teams reinforce this hatred. His entire worldview and political bent are created from this persecution. In Atlas Games' Over the Edge rpg, this is called the Throckmorton Paradox.
Paradox 5) Timetravelling assassins try to kill Hitler. Interrogation and torture of the assassins provide a rudimentary understanding of the mathematical theory and/or mechanical instrumentation of time travel. A fortune of resources and manpower is attached to timetravel research, but the mathematicians and intellectuals who could have fathomed the notes have all fled to Britain or America. After the war American, British, French and Soviet thinktanks using captured German scientists and recovered document troves build on the German's crude attempts at timetravel. Eventually one of them succeeds and builds the early prototype of a functional time machine. The others use their spies to steal information so they can catch up. This forms a club of nations that have timetravel. The fear of a neverending time war leads to the nations refusing to use timetravel. Eventually the end of the Cold War and advances in technology means individuals can build crude timemachines. A group of idealists build a timemachine and try to go back in time to kill Hitler. They fail and are captured, interrogated, and tortured to death to find out all they know. The Nazis start work on a timemachine...
Paradox 6) Timetravelling assasins go back in time and successfully kill Hitler. When they return to the present subtle or radical changes have occurred due to Hitler's death. Perhaps another autocrat rose to power and World War Two happens anyway. Or America remains conservative and isolationist, stays out of the conflict and World War Two ends quickly with the victors becoming politically ascendant. See A Gun for Dinosaur by L. Sprague de Camp.
