An interesting thought:
A superweapon more powerful than nuclear weapons might with a single use cause the end of life as we know it. As such, you would not test or demonstrate it, therefore the weapon might not be useful.
No, the "better" superweapon would be about precision and speed of destruction... like the ability to resolve the whole surface of the planet at sub cm resolution and pick out and destroy any target in moments... imagine a starlink-type constellation but spy satellites with space lasers instead backed by enormous AI facial-and-other recognition to identify where anybody or anything was. Or maybe something like being able to read thoughts at a distance or even influence them.
A bigger bomb though is just about doing something we can already do slightly more quickly. We can also already build bigger bombs than we have but there's no strategic advantage.
We have that, it just doesn't work quite the way you think. One of its many manifestations is called "Twitter".
This isn't a joke. Consider the conventional notion of a mind control device, a magical mind-laser that can target one person at a time from a distance and modify their thoughts or even beliefs. Compare to what a motivated billionaire could accomplish, today, using paid botnets and content farms.
Today's version is wildly more influential, can not only change beliefs but also inoculate the targets against future influences in the other direction(s), and operates at a mass scale. It is so successful and effective that it doesn't even need to be kept secret like the usual scifi version.
The only thing exaggerated in my description is that it doesn't require the resources of a billionaire. You can operate it for far less.
We need an adaptation of Arthur C. Clarke's "sufficiently advanced technology" quote.
Possibly with a human in the loop for final confirmation, which receives a target image on the screen for engagement approval. One human could approve hundred of hits per hour if you don't want to go fully autonomous.
Of course, the ability to automatically defend against drones/robot dogs will be next.
But to the main point, a nuke-like powerful bomb without radiation fallout would be quite valuable.
Taking that idea to its extreme (and while we're discussing an article about potentially exotic physics) a superweapon (or superpower) could be simply "teleportation".
If you could trigger the creation of two ends of a wormhole to appear at arbitrary points in space (without needing any equipment at either point), you could teleport remote photons from your enemy's territory into your research station, which would effectively give you an invisible spy camera that can view anywhere on Earth in real time, allowing you to track all the military hardware and personnel that the enemy has.
An attack would involve (re)moving a few grams of electronics or neurons from the target, and would be almost invisible and unstoppable.
Even if the wormhole had to be "sent" using something like a portal gun, that would still dramatically change the dynamics of the battlefield.