Chapter 137 has some interesting stuff, always wonder how powerful ppl below lvl 800 was, and we got a definitive answer for all of it.
Once thing is clear now, Ruphas vs Benet was an outlier for Benet, always seemed odd to me that Benet could put up a fight against someone double her level when the level increases certainly aren't linear.
Interesting parts about levels:
Level 4-10
In terms of Earthlings, level 4 would be at the level of a professional martial artist. The strongest amongst them might become a world champion, however, there would be barely any differences in terms of their status. An Earthling who could reach level 5 would probably be the rarest of the rare.
Level 201 ― 300
A walking strategic-level weapon. If they run, they would be able to move faster than the speed of sound. Their arcane magic would be able to burn down an entire forest. Their sword attacks would create fissures in the land itself.
With their strength, they would be able to fight against Earth's large army of battalions alone. (But not against nuclear weapons!)
Level 301 ― 500
Individually, they can easily surpass a kingdom's military might and change even the weather.
If these individuals were to get serious, they could even completely erase a small area of land. They can fight against the entire Japanese defence force in a frontal assault on equal footing. Still assuming no nuclear weapons.
But if they're over level 400, there is a possibility that they can withstand nuclear strikes.
Level 501 ― 700
They can split seas, crack mountains and change the very geographical structure of the planet.
These people should be thought of as catastrophes that possess a will of their own. They are no longer existences that can be handled by means of common sense. By this stage, not even a small scale nuclear weapon would be able to defeat them. Level 701 ― 999
Major catastrophes. Individually, they can destroy civilisations. Let alone that, they can even wipe out all living creatures on the planet. Truly monsters.
By this stage, even if the Earth's strongest nuclear weapon directly hit them, they will not die.
Level 1000
The pinnacle of strength. Individually, these people have the strength to turn a planet into a dead rock..
They are at the point where "even after striking them with all the nuclear weapons the world has, they finally suffered some small damage" stage.
Level 1500 Alkaid
A bit more specifically, it is possible for them to deal more damage than a planet like Midgard would be able to bear and shatter it. Furthermore, damage limits go up by one digit for every one thousand level threshold that they break past.
At this stage, they can fight at half the speed of light. From a single jump, they can reach space and with a single kick shatter a planet.
Even a mere shockwave of full-strength arcane magic will shatter countless planets and can even cause cosmic-scale explosions.
Level 3000
The stage where nothing makes sense anymore.
If they feel like it, they can probably destroy a solar system at the very least. (Half-assed statement)