Power Copying (especially the Power Parasite variant) when it doesn't have limits to how much it can copy.Pals with Jesus, when the "Jesus" in question is at a higher power level then the rest of the cast and is willing to help you unconditionally.A One-Hit Kill attack that has no true way to resist and/or a limit to how powerful a target can be affected by it.Nigh-Invulnerability, you can try and hurt the person, but to them it's like a small poke.If it has a Your Mind Makes It Real component, even more so. Master of Illusion, as a person with enough creativity and power over hallucinations and other such trickery could get away with whatever they wanted to, especially if their target doesn't know that they have such powers.Mind Control/ Brainwashing, especially when employed en masse or without immunity.Meta Powers, as the ability to influence another person's powers without limit can make a character nigh-unbeatable in a fight.Memory Erasing/Modifying powers, especially when there is no limit to how much of the target's memory you can erase or modify, meaning you could potentially make them not even the same person anymore.Intangibility, especially when the character can't be attacked or restrained in any way, and/or they can still affect the physical world while intangible.Imagination-Based Superpower, if there isn't a sufficient limit to what the character's imagination can create under the rules.Energy Absorption if the user can absorb and fire back any amount of energy they wish.Any convenient way of bringing people Back from the Dead.An Attack Reflector that can reverse even the strongest attacks with ease.Anti-Magic or its equivalents in a setting where magic is used frequently.Adaptive Ability that makes the character immune to a power after being hit with it once.The abilities most likely to be Story-Breaker Powers without careful use are: This is why most stories with such villains focus on stopping them from actually getting these powers. Though this isn't to say it's good for a villain to have a Story-Breaker Power, because they run the risk of becoming a Villain Sue. On a bit of a tangent, there's a reason why this trope applies mostly to protagonists we expect the Big Bad to have a nigh unbeatable edge and get beaten nonetheless, giving us a typical underdog story. Power Creep, Power Seep works similarly, but specifically kicks in when the character is an alternate setting/timeline or is being handled by a different author, and their usual capabilities would break the story intended for them. If for instance a character, with all their Super Strength, is often shown being able to stop calamities like falling buildings but is suddenly shown to struggle dealing with the villain's Mooks, this trope is likely at work. Another good sign of this trope affecting the setting is if over time, it seems as though the character's abilities and competence can suddenly fluctuate in a non-intuitive way depending on the plot.