Let me address the most important thing first, since many seemed to be confused: Angels and Demons.
I'll make sure to keep it compact and brief so as not to waste anyone's reading time.
Important to note that Angels and Demons are only titles, occupations, not actual Angels or Demons. Angels are Supernals who worked in the sky—while Demons are Supernals who worked underground.
Supernals are measured and dictated by their potential to grow stronger, as there are quotas for every single divine bloodline. Measuring their potential is done through counting their Divine Locks inside their bodies. Those with five or below Divine Locks would automatically become an Angel, while those with more can choose to become a Demon or Angel.
Those with five or below Divine Locks are basically INCOMPATIBLE with their divine bloodline, as the divine bloodline blessed a newborn randomly, thereby having less potential. Gods DO NOT control where their bloodline went but gave mankind the liberty to manage it instead.
Someone's potential CANNOT change; that's the well-known fact. (Except for MC, of course.)
And as I said, there are quotas for every divine bloodline; so there's a LIMIT to how many Supernals with the same divine bloodline at the same time.
This is where the stigma that Angels are worse than normal humans, despite having power, comes from.
Let's use an example:
Hades, the God of the Underworld, is a powerful Olympian God. A Supernal with His divine bloodline would undoubtedly be extremely strong. But he has a quota of 10 Supernals—meaning, there can only be ten Supernals with the bloodline of Hades at the same time in the whole entire world.
So, when someone is identified to be a Supernal of Hades—but only has two Divine Locks, they are basically HOGGING one quota of Hades, wasting the God of the Underworld's bloodline, which would be better to be inside someone with a higher compatibility with that bloodline.
That person would need to DIE before that one quota of Hades he hogged could be recycled—and given to another newborn who might be more compatible. So, that's why Angels are considered 'WORSE' than being a normal human, as they are actively wasting a quota of a divine bloodline, which was mankind's weapon to fight the Blue Void, and guarantees a bad future for mankind.
And this is also why the academy for Angels was tailored to be depressing, encouraging them to DIE, as that would be better for mankind. Angels who wanted to LIVE would need to perform—for mankind and be useful.
Naturally, since the main character, Kai, only has ONE Divine Lock thus branded—as a Lesser Angel, he was the one encouraged to die the most.
One more thing: some of you are confused as to why the other Angels viewed them as higher than Kai despite Kai being stronger. And that's because they thought they have more potential. In their minds, sure Kai could be stronger than me right now—but sooner or later, he would fall behind. And despite knowing that, he dares act mighty in front of me?
That's basically how they think.
Little do they know, Kai has a Primordial Lock, not a Divine Lock. And his potential has no ceiling.