MarvelCosmology

The Phoenix Force is the sum and substance of life, hopes and dreams in the total omniverse. And despite it being famously known and depicted as a bird entity made of fire in the comics, even that itself is an avatar and the true Phoenix Force is actually the entire dimension of the White Hot Room itself (also known as The Mystery).

It can house the multi eternities, including the First Firmament.

It powers the concordance engine of the Beyonders, and essentially them also.
It is even transcendental to the Beyond dimension.
The Beyonder says against the pure phoenix force, he is outclassed.

Could hold the true celestials and bring them forth out of the Fifth Host by rebirth.

[To find out more about White Hot Room, check out The Mystery.]

Because most, if not all, the stuffs about Phoenix Force comes from its avatars, this page will be broken down into two sections:

The Phoenix avatar

According to Hank McCoy, the phoenix avatar's power defies measurement.

A small sliver of the phoenix's fire could blow up a planet, scatter the atoms across the cosmos and rip someone apart at a subatomic level.

A containment field built specifically to negate the PF energy couldn't do so.

Binary Carol, being powered by a white hole that was giving birth to an entire universe, felt like she receded to a pinpoint while simply trying to absorb the Phoenix avatar. She also exceeded time and space.

A small portion of the phoenix avatar was causing multiple time-quakes, reality warps and the multiverse collapsing in on itself. Roma couldn't comprehend either the purpose or the entity causing these.

The avatar of Phoenix makes a lighthouse exist in all the planes of the multiverse simultaneously.
Then creates the Energy Matrix that powers the Otherworld (pandimensional).

Charles Xavier simply coming in contact with the Phoenix inside Rachel gets stuck in an illusion for 10 hours and gets his memory erased. Also blocked out Jean Grey from helping him.

Mar Vell being amped by the Phoenix avatar could see thru 17000-D.

Jane Thor felt the heat of the PF avatar from galaxies away and it began to melt her soul.
The Destroyer couldn't do anything to the PF and got one shot.

When Doom tried to destroy the entirety of Limbo, Phoenix (a fraction of the Phoenix avatar masquerading as Jean Grey) telekinetically holds the entirety of the dimension together [Limbo is pan dimensional].

The Phoenix hosts

Just being imbued with portion of the phoenix force lets the entire cosmos through Hyperion and stretches his mind out to infinity.

Can reduce someone to their very essence to the point they can't ever reform or come back.
Also lets its host be acausal.

Jean as the phoenix host could "amputate" an entire future timeline out of existence effortlessly.
Could hold an entire universe in her hands.

A portion of the phoenix avatar in an alternate timeline Vulcan was going to consume all of reality.

Giraud as an avatar of the phoenix force could inflict pain on Eternity.

Necrom as an avatar of the phoenix force is able to compress infinite amount of universes into one singularity.

Rachel with the PF kills Necrom with the PF and scatters him throughout infinity.

The Excalibur team all fused with each other uses Rachel (phoenix)'s power to rise through the planes of the multiverse.

Rachel as PF host casually blocks an attack from a hungry Galactus.
And then fights and beats hungry Galactus.

Xavier and Dark Phoenix has a psychic battle that spans all the infinite planes of existence simultaneously.

Ilyana with the PF raised and merged a portion of Limbo into the earthly plane.

PF cyclops tears thru dimensions to arrive to Kun Lun.

PF cyclops no sells Wanda who gave "everything [she] had" (Wanda's chaos magic at its height could tear the entire multiverse's continuum to bits, destroy all the dimensions of the pan dimensional Otherworld, one shot Roma in the process, breach the boundaries of causality, erase the concepts of chaos and order and was going to turn all of creation to a conceptual blob. All of this was from a single spell).

Cyclops simply turning into his Dark Phoenix form was causing Earth to tear apart all over (Earth & Sun).

PF cyclops could grow large enough he hit the White Hot Room.

Logan as a PF avatar holds back an entire multiverse for a prolonged period of time.

A dying Starbrand with the energy of the first PF avatar (who was also almost burnt out) creates 615 universes.

Phoenix wielders never die.