It's awfully hard to beat an ability that allows you to hit someone before the fight started, or to hit them in the future when they can't defend. It makes zero sense, but that's how it goes. In Creatures of Light and Darkness it's presented as pretty much a fight-ender (and it is).
However, in two of the most important fights in the book, the main character does battle against:
1. Another Fugue-user;
end of spoilers.
Needless to say, in these two plot-critical fights Temporal Fugue isn't the big game-winner it should be.
"Gendou is probably the least whiny, but... well, let's just say that his reaction was probably not quite as healthy as a good whine."
-The Drunkard Kid, on Evangelion
But it's not just 'Temporal Fugue, I WIN!' He's winning on due to being Set (part of which - only part - is him being a master of Temporal Fugue), and being tricked out with some of the best gear one can find in fantasy/sci-fi.
Whereas he has another fight in the books against a top-end immortal, basically says 'Screw this, Temporal Fugue, go!', and then the fight is over. Three seconds ago.
The longer Max Damage is awake, the more powerful his invulnerability. But if he is asleep or woke up less than an hour ago, he is pretty damn vulnerable to harm. Or if he stays awake for a few days, he is going to get careless or even delusional from sleep deprivation. Or else suffer side effects from using drugs to stay awake. It's powerful but balanced.
Regarding Temporal Fugue... I've seen it show up twice in pen and paper rpgs. In the original Metamorphosis Alpha, it was a mutation. IIRC, it just gave you a few temporary clones for a fight. In a couple of weeks, we will be trying the modern Gamma World (d20), and one of the other players got a combination of Time Travel and Clone, which sounds like Temporal Fugue, more or less. I will be playing a Pyrokinetic Speedster, so hopefully speed kills in Gamma World like it does in Rumbles.
"Injustice anywhere is a threat to justice everywhere."
Martin Luther King Jr., Letter from Birmingham Jail, April 16, 1963
There's an ability in Don't rest Your Head that lets you warp reality by speaking the language of God.
It's not truly broken at first, because you need to learn the language to do specific things, gain power and whatnot.
Later on, the only real limitation is that you need to speak pretty much.
“You know what the best thing about magic is?
Fiamma of the Right had a pretty sweet ability.
The Holy Right, which manifested as a floating Third Arm above his shoulder. It could strike instantly, annihilate things without destructive force, and serve as an auto-shield. Plus it allowed him to do anything done with the right hand in Christianity.
It even blocked a laser satellite shot that Fiamma was caught off guard by, and destroyed it with one swipe even though he had no clue where it was.
Unfortunately, it's not very good on feats, but its only weakness was that it could be used a limited number of times before it became permanently unusuable. But Fiamma temporarily got around it by using Imagine Breaker as a physical form so the Holy Right could be used infinitely.
In particular, Dave used his time travelling powers to be in multiple places at once by traveling back to a time he knew he would be in. When the others talked to him they never knew from which point of his personal timeline he was speaking from, so sometimes he'd know things that hadn't happened yet. This allowed him to get a ton of stuff done, and even interact with and work together with past and future versions of himself. Aradia, the other Time user, created a whole army of her own time clones this way.
The downside is that Homestuck is heavily fatalistic in theme and the laws of reality only allows for one timeline to exist. There is no changing the future or going back to correct mistakes - anyone deviating from the alpha timeline is doomed to die shortly afterwards. The only way to use Time Shenanigans safely is to make sure each time clone moves through a stable time loop, so that the alpha timeline remains unbroken. That is to say, Dave can't do anything he knows contradicts what one of his future selves will do. If he does, a lot of dead Daves start piling up, and Dead Daves Are The Enemy.
"This doesn't look easy. But I bet it is!"
"Optimism through stalwart skepticism is a defect not everyone is lucky enough to be cursed with."
Yeah I give up. They would need like a bajillion UNs to take it out. And they would all have to work.
Hey, if OCs are allowed, I suddenly remembered one: Johnny Lash, aka Backlash.
Johnny has the abilityto reflect all forms of attack and negative affects back at the attacker, regardless the nature of the attack, be it direct or indirect. For example, shooting him with a gun will cause the bullet to appear inside the shooter. Trying to rip the air out of his lungs will instead cause the air to be ripped out of the attackers lungs. Even throwing him into a wall will cause the thrower to take damage instead, and trying to trick him into damaging himself will only cause the hazard he’s stumbled into to take the damage. This is an always on defensive ability that thus far has absolutely no flaw or weakness, and can even backfire the attacks of gods. He is even one of the extremely few superhumans completely unaffected by Zero Metal and other power neutralizers, and power replicators cannot copy his power. However, anything that would prove harmless to Johnny can get through, so he can take drugs and enjoy the mind-effecting benefits without suffering any negative side effects, can have sex without the pleasure being redirected, eat junk food and never have health problems, etc.
There are two downsides to this power however: Firstly, he cannot benefit from stat-boosting abilities, magic, chi, tech, whatever. Ergo, strengthening spells, speed boosters, etc. cannot empower him. He likewise is not effected by healing spells or the like (not that he really needs them). He could pick up Thor's hammer because he'd reflect the spells that prevent it from being lifted, but it would be no better than a normal battle-hammer in his hands, and he likewise couldn't prevent it from just getting pulled away from his grip by Thor.
Secondly, the bigger problem with Johnny’s power is that he has no offensive ability to speak of. Attacking, much less defeating, a superhuman literally requires him to get attacked by them and hope that backfired attack can put them down. Even though he can backfire the attacks of gods themselves, by himself, the best he can do is just punch someone with a normal human punch or shoot them with agun. In addition, the easiest way to beat Johnny is simply to pin him down or trap him. He only has normal human strength, so even something as simple as tying him up, or locking him in a cage will take him out of the fight, as will literally throwing him away from the fight. Ergo, Johnny is actually more dependent on his superhuman minions to take the offensive than he would like to admit.
Considering his primary enemies are a team of Avengers-level heroes, Johnny finds his powers may protect him, but he has no real use on the battlefield. He's not even that good of a fighter. His usual battle tactic is to have one of his speedsters pick him up and zip him around the battlefield to intercept enemy attacks, but that only lasts so long with three of the enemies themselves are speedsters, too.
It's a lie! My pants were off the entire time!
Kakeru Hase's Perfect World from Psycho Buster.
Most people probably recall me describing it in another thread, but here it is for the others:
Kakeru's Perfect World can be set up in a zone around him (initially ten meters, later city-sized).
Within that zone, Kakeru is the 'editor' of the world as if it was a movie. So he can pause, accelerate, rewind, move stuff, remove stuff and so on.
He can also do things like keep kinetic energy in place while he rewind, so that instead of giving one punch, he gives a hundred punches simultaneously.
He can also individually rewind timelines, to make it so that one person hasn't died, for example, while everything else stays the same.
Already pretty ridiculous.
Perfect World also triggers instantaneously if Kakeru dies, and then rewinds time until he isn't dead and stops it.
And it can't be prevented by power nullification.
Now, that is broken. And in Rumbles it is.
In-universe, it isn't that broken, just absolutely overwhelming.
Because using it will eventually lead to space/time collapsing and destroying the world.
So yeah, in-universe Perfect World pretty much defines "Too Awesome To Use".
Suffering is a fact of life. You survive if you find a reason to endure it.