One

One is a light blue Arabic numeral 1. One's color is similar to that of Four's, albeit slightly paler. She is armless, unlike the other algebralians. On some occasions, One's eyes appear slimmer and more tilted, including when she is enraged.

One is nonchalant, calm and seems helpful, but is very manipulative and malicious under the surface. She seems to constantly observe the contestants and knows their vulnerabilities very well, which she exploits to convince (or blackmail) them into signing her deals, often for rewards she may or may not actually give. One is easily irritable and gets annoyed when people are hesitant or resistant to her and gets enraged when people defy her like Donut and Leafy do in "Last One Standing", and follows through with her blackmail or otherwise punishes them severely. It is suggested that these deals involve One taking full control over them, as it was phrased as them “signing themselves away”, and she said someone on the list (of signatures) would disappear if Donut kept refusing the deal. She is also very power-hungry, conspiring to take Two (and later Four’s) power and gleefully fidgeting with it when she finally gets it in "Last One Standing".

Get Two's Power: In "Last One Standing", One finally got not only Two's, But also Four's Powers from Pencil, allowing her nigh-omnipotence. Succeded "Last One Standing" Wreak Total Havoc: After the events of TPOT 19. One begins destroying planets, slicing the Really Weird Planet in the Orion Nebula in half and kicking Earth far away from the Sun, plunging it into darkness. Succeeding/Ongoing TBA

Anomaly removal: In "Seasonal Shift", she was powerful enough to restore the entire world back to a more stable state before the Rift in Space-Time opened, probably by making it as if most the time traveling never happened. (However, since the rift itself was just reduced to a more manageable state for Black Hole, it's likely either she wasn't strong enough to completely fix it, or she didn't fix it on purpose to use the rift as leverage on her future victims. This seems more likely since she was completely fine with endangering all of existence since she is completely safe within her dimension.)
Atmokinesis/Weather Manipulation: In "Category One", with her ability to warp reality, One can change the weather and create storms to cause havoc.
Chronokinesis/Time Manipulation: In "Last One Standing", One is revealed to be able to remove people from existence, some of these include: Basketball, Gaty, Barf Bag, and Pencil (possibly).
Teleportation: One is able to teleport herself and other people as seen in "What's Up Bell's String?".
Super Speed: In "What's Up Bell's String?", during the Team Swap, One runs around shuffling the contestants, finishing in just 17 frames, or less than a third of a second, all while Two is looking away. By the time that someone says something, One has jumped back into the bush, leaving Two and all of the contestants oblivious to what happened.
Conjuration: One can create objects out of thin air, as seen when she conjures a document for Fanny to sign in "What's Up Bell's String?", creating body parts to offer Ice Cube and Fanny, or in "Seasonal Shift", where she creates a remote while talking with Gaty to show her what happened to the eliminated contestants she took.
Pocket Dimension: As seen in "What's Up Bell's String?" and "Category One", One can create pocket dimensions and manipulate the contents at will.
Black Hole Immunity: As One was shuffling the contestants, she moves Black Hole effortlessly without being warped by his gravity.

Technology/Electricity Manipulation: As seen in "Category One", One is able to manipulate Robot Flower's mind to go back to her previous self, and it's implied that they're also capable of making her personality even more destructive. She can also appear inside screens, as seen in the beginning of "Seasonal Shift".
Reality Warping: One has the ability to change, create, or even destroy parts of Dreamier Island, Grasslands, and possibly any other places indirectly only by using a miniature of the location she wants to warp in her dimension. She is also able to make the rift in space-time shoot out reality-warping lightning bolts via her miniature in "Last One Standing".
Anomaly removal: In "Seasonal Shift", she was powerful enough to restore the entire world back to a more stable state before the Rift in Space-Time opened, probably by making it as if most the time traveling never happened. (However, since the rift itself was just reduced to a more manageable state for Black Hole, it's likely either she wasn't strong enough to completely fix it, or she didn't fix it on purpose to use the rift as leverage on her future victims. This seems more likely since she was completely fine with endangering all of existence since she is completely safe within her dimension.)
Atmokinesis/Weather Manipulation: In "Category One", with her ability to warp reality, One can change the weather and create storms to cause havoc.
Chronokinesis/Time Manipulation: In "Last One Standing", One is revealed to be able to remove people from existence, some of these include: Basketball, Gaty, Barf Bag, and Pencil (possibly).

Nigh-Omnipotence (from The Power of One): One has shown to possess near limitless levels of power, However she states herself to be seemingly weaker than Two and by extension Four, in her line "I do have power, but not enough", and her entire reason of offering deals to the contestants is to gain Two's power. However, even without Two's power she is still unimaginably powerful. She is shown to have near unrestricted control over fundamental forces including space, time, matter, and energy, and is seemingly able to grant any request made in her deals, like granting a person new limbs or restoring someone's original personality. However, One truly shows how powerful she can be in "Seasonal Shift" when she returns reality to a more stable state before the rift in space-time opened, seemingly with just a snap. Overall, One has been shown to be able to do nearly anything anyone could imagine, showing that while she may (supposedly) fall short in power compared with the likes of Two and Four, she is still a godly being in her own right.
Super strength and/or telekinesis: In "Outbreak At Stake", she may have kicked a hole through the Moon in the second post-credit scene, or she used telekinesis to break a piece of it off. In "What's Up Bell's String?", she used telekinesis to hold Fanny's new mouth and the contract list. She is also able to easily kick the Earth away in "Last One Standing", though this was shown after she gained most of Two's and all of Four's powers by Pencil.
Nigh-Omnipresence: One can be seen being in some of the contestant's dreams and hiding in plain sight in certain scenes. The contestant's dreams include: Black Hole, Pen, Winner, Barf Bag, and Book, but One is still in reality, meaning she can be in multiple places at the same time.