I made a simple classification system to use in my Paragons setting. I would like to hear your ideas on the subject. I used the word "nova" for superhuman while writing this.
Z-Class: These are the least powerful of all novas. They have only one minor, irrelevant power, like flying at speeds lower than 40 km per hour or telekinesis that can lift only few kilograms of mass.They do not pose a threat any more than an armed baseline human does and can be subdued by armed forces easily.
D -Class: These novas have one power or few powers of low level. They can be a threat to society but they can be taken down by standart military units.
D-class novas can lift up to 10 tons,resist gunshots for a limited time, reach speeds up to 500 mph and have the firepower of a rocket launcher. A nova who can teleport to anywhere in the world but a normal human otherwise would count as D-class too.
Comic book examples: Cyclops from X-Men. Reed Richars from Fantastic Four also fits in this level.
C-Class: Few powers of moderate level defines C-class novas. Only military units with special equipment and armored vechiles can stop novas of this power level, also collateral damage is nearly certain in such a battle. They are called capes in slang, since they are at the same power level as most comic book heroes.
C-Class novas can lift up to 100 tons of weight (weight of a Boeing 767), stand unaffected by gunfire, have the firepower of a tank cannon and move at speeds up to 1000 mph.
Comic book examples: Luke Cage.
B-Class: Novas with high level powers and usually some versatility are called beta class. Versatile but not powerful abilities like shapeshifting into human or animal forms, transforming matter on a small scale also qualify for B-class. They too are often called capes.
B-Class novas can lift up to 1000 tons of weight (weight of a small bridge), withstand tank cannons, have the firepower of a battleship cannon and move at speeds up to 5000 mph.
Comic book examples: Colossus from X-Men.Iron Man with standart armor.
A-Class: These novas have very high level powers . They can affect large areas. They excel in their fields and might have diverse powers. Novas with only one but a very versatile ability like shapeshifting, precognition, transforming tons of matter or mimicking the powers of other novas for a long time are also in this category. There are only few dozen novas of this level in the world. They are called alphas, since they are the dominant class of novas, with the exception of epics.
They can lift up to 10000 tons (weight of a cruiser ship) move at at speeds up to 10.000 mph and withstand shots from battleship cannons.
Comic book examples: Thor. He is extremely strong and durable. He can call lightning bolts and control weather.
Epic Class: They have powers at incredible levels. It is more logical to determine lower limits of their power than upper limit. They can affect immense areas. The diversity of their powers allows them to fulfill more than one niche. Unlimited shapeshifting, ability to totally mimic other novas’ powers indefinitely, transforming hundreds of tons of matter can be seen among epic novas.
Comic book examples: Superman with his physical might, agility, flight, laser beams, incredible senses and superhuman intelligence.
Silver Surfer has durability of highest order, can boost his strength to incalculable levels, hit targets in orbit from earth, project and absorb every kind of energy, transform literally mountains of matter, heal people, fly at faster than light speeds, detect matter and energy from light years away…
I divided power level into five division in 2e game terms too. Speed powers do not correlate with this ranks, they are exception.
Low-Level Power: 8-9 rank or ability modifier
Moderate Power:10-12 rank or ability modifier
High-Level Power: 13-14 rank or ability modifier
Very High-Level Power: 15-17 rank or ability modifier
Epic-Level Power: 18+ rank or ability modifier