Cyclops may not be an Omega-level level mutant, but he once controlled the full power of the Phoenix Force and used it to change reality. In Jason Aaron, Brian Michael Bendis, Ed Brubaker, Jonathan Hickman, Matt Fraction, and John Romita Jr.'s Avengers Vs. X-Men, the X-Men's veteran leader was first granted a taste of the Phoenix's power when the Avengers intercepted the cosmic force as it approached Earth. Iron Man attempted to create an armor capable of neutralizing the Phoenix. The effort split the Phoenix Force into five pieces, which attached themselves to five separate X-Men: Cyclops, Emma Frost, Magik, Colossus and Namor.
Although some chose to use the new power simply to conquer (Namor in particular), Cyclops wanted to reshape reality in a way that would benefit mutants. While this aspiration began as a noble intention, the absolute power of the Phoenix corrupted Scott, ultimately turning him into a new incarnation of the Dark Phoenix. The cosmic force simultaneously increased his already formidable optic blast to immeasurable levels and granted him new abilities such as telepathy, almost limitless telekinesis, and the power to fly at incredible speeds.
In order to reshape reality, the Dark Phoenix uses a power that can be best described as molecular reconstruction, allowing it to manipulate the fabric of the world around it. A power such as this is only enjoyed by the most powerful beings, such as Molecule Man and God-Emperor Doom.
Durability is also one of the Dark Phoenix's specialties, using abilities like energy absorption, immortality and resurrection to ensure it is almost undefeatable. The most visible power of the Dark Phoenix is pyrokinesis, keeping in theme with its image signifying the fiery cycle of death and rebirth. Although Cyclops had access to a lot of these powers in his initial transformation into the Phoenix, it wasn't until his transformation into the Dark Phoenix in Avengers vs. X-Men #11 that he was able to exhibit them all.
Of the five mutants imbued with the Phoenix Force during Avengers vs. X-Men, Namor was the first to fall. The others discovered that when one of them fell, their power was redistributed among the remaining members. Colossus and Magik fell to one another later on, leaving only Cyclops and Emma Frost.
Cyclops, having been slowly corrupted, turned on his lover and stole her portion of the Phoenix Force, finally becoming fully powered. Scott's new god-like power drove him to his very limits, twisting his mind. Professor Xavier stood up to Cyclops, hoping to appeal to what was left of Scott. Unfortunately, Cyclops was too far-gone, and he gave in to the Dark Phoenix and killed his mentor.
Although Cyclops' wielding of the power of the Phoenix ended up being temporary, it still marks a time that his power levels excelled to a point well beyond the limits of even Omega-level mutants and made him one of the most powerful beings in existence for a time.