Exaggerated: The situation has gotten so bad that ending it by killing 99% of the world's population and reducing the remaining 1% to Stone Age technology is actually better than allowing it to continue.
Can be Truth in Television in Real Life, at least in its more individual variants (extreme medical treatments, self-defense, the attempt to stop/mitigate a major disaster)
The consequences of the action taken may be bad, but the results of not acting really woukd be that much worse. Would you rather sacrifice two cities to end a problem, or lose three and still have it out there?
The situation can be resolved via interventions that are cheap, simple, and cause little or no lasting or permanent damage or death or destruction. It is the exact opposite of crossing the threshold, and anyone who invokes an option that does cross the threshold in it anyway has crossed the Moral Event Horizon and committed anything from medical malpractice to murder to a war crime.
Can be Truth in Television in Real Life as well. Part of the point of many investigations and lawsuits is to determine if such an inversion happened - if someone didn't stop to think of less dangerous or violent solutions to a situation.
The situation really is that bad... but the solution is even worse, so it's better to let it continue than attempt to stop it.
The situation looks as if it has crossed the threshold, but it has not at the moment or will not, and there is a solution that, while not necessarily harmless or cheap or simple, is also not as or more horrible in result than what is happening. For example, the cancer can be cured with surgery alone, or the nuclear reactor's last failsafes work well enough that it successfully shuts down just before core meltdown, although restoring it to actual safe use will be an expensive, long process.
The solution ends up with a ridiculous consequence such as everyone turning purple.
The severe solution solves the problem but spins into unintended consequences such as more wars, the Cycle of Revenge, or the like, which themselves cross the threshold demanding equally severe solutions.
The problem crosses the threshold briefly but then goes back to being less severe.
The problem never happens or gets near the threshold, due to cooler heads prevailing, failsafe systems that work, the proper preparation preventing it, or similar.
Can be and often, thankfully, is Truth in Television in Real Life: the reason for safety measures including failsafes where needed, regulations requiring preparedness or safety measures, and similar is to prevent problems such as this, and in at least one Real Life case, global thermonuclear war itself was prevented by someone staying calm and verifying a false alarm as such.
In almost all fictional media where something reaches the threshold, for the reasons mentioned in the main article.
In Real Life, any use of a nuclear weapon (and to a slightly lesser degree, the use of biological or chemical weapons), and the overt commission of genocide by an identified nation/state all are the threshold codified into international law and policy: any nation/state found to be currently engaging in such conduct can expect a declaration of war as the response.
In Real Life on a more individual level, pulling a gun on someone in many places is the threshold enforced: by doing so, you have given them the legal right to kill you in self-defense, even if you don't fire.
In Real Life in general, any situation where the inevitable or near-inevitable outcome of not dealing with the situation or of using less severe solutions is the loss of human life (especially if it's the loss of multiple lives) is usually this to some degree: almost any amount of property damage, injury, or even death is considered worth it to prevent someone from dying or to prevent someone or something from killing more people than it already has. For example, amputating someone's legs or putting them through chemotherapy or giving them an ongoing drug addiction to save their life, or demolishing a neighborhood to create a firebreak against a superfire or dumping seawater on nuclear reactors - because the alternative is far worse.
"You are telling me we should drop a nuclear bomb on the oil well? What next, summoning Godzilla?"
Discussed: "I hate to do this but it is the only option we have."
Conversed: Bob and Alice watch a show and mention how desperate the heroes must be to come up with such a plan.
The heroes find a solution that results in many deaths and are considered international criminals despite defeating the Big Bad.
The heroes find a solution that works, but now they're stuck with finding a way to deal with the aftermath of said solution, which is just as bad as (if not worse than) the previous problem.
Reconstructed: They turn themselves in, the jury looks over the evidence, and find them innocent of charges since the alternative would have been far worse.
Played For Laughs: Their solution will result in the destruction of one of the heroes' favorite restaurants. He finds the act horrible and almost decides against it until the other heroes give him a Dope Slap.