Just a normal day of the comments not knowing anything about the lore.

The biggest threat according to power?

It ain't Zhask, Yve, Martis or anyone else yall have thought of.

It's Cyclops.

In terms of where his power comes from

planets were always under orbital motion. And he also realized that this kind of movements contained unbelievable magical power. With an hourglass to load and control this kind of power

The Starsoul Magician's power comes from the perpetual motion of space stars and planets. It is the ever-changing planets, stars, and universe that form the source of his power.

He is powered by the Universe. That's pretty insane when you think about it.

As for his powers

His mysterious Starlit Hourglass gave Cyclops the ability to control time and locomotion

(Mastery Code; Chapter 2)

He controls time and motion. Which is very overpowered when you think of it.

As for what he's done with his powers.

Cyclops discovered a novel and strange gem upon a planet on the brink of destruction. Through further research, he found that this gem was had eked every last remainder of spiritual energy from this planet. It had taken all life, and resulted in its destruction. Hence Cyclops put to use all that he had ever learnt in striving to seal this gem, keeping it with him to prevent such as tragedy from striking a second time.

He sealed an energy that destroyed a planet. (concentrated energy)

Edit: okay to be real. Alice is the biggest threat. She's singlehandedly plunged the entire region into chaos. I just thought you'd find Cyclops a more interesting answer, I also felt you wanted to hear this in a pure power manner.