Superhuman Physical Characteristics, Irregular Physiology (Monsters physiologies show they are mostly made of magic, noting that humans have a "physical form"[2], along with having their SOUL directly attuned to their body[3]), Magic (All monsters are made of magic, being able to do things like make "bullet-patter cards" with their magic[4]), Personal Domain & Battlefield Removal (When one encounters a monster they get into a fight, a FIGHT is an encounter in a monster's personal domain allowing them to fight humans, this has various rules such as turn-based combat), Creation (Monsters can make weapons, clothes and even food from magic), Limited Spatial Manipulation (3-D; Monsters can at times influence the battle box), Transmutation & Healing (Monsters can turn their attacks into healing projectiles), Absorption (Monsters and humans can absorb the SOUL as long as the person isn’t the same species as them), Curtain Fire, Soul Manipulation & Essence Manipulation (All attacks in Undertale are to the SOUL).
Resistance to Physical Attacks (All monsters bodies are attuned to their SOUL thus only attacks that can affect their SOUL can affect them[5]), Soul Manipulation & Essence Manipulation (Can take hits to the SOUL)
Genius Intelligence, Instinctive Reaction (In the form of personal domain Sans can dodge any attack under the fight system, even if he's asleep while one is actively breaking the rules of the personal domain requiring one to completely go agains the rules of the game to even hit him), Enhanced Spatial Manipulation (Can completely control the battle box, to the point where he can change it's size, move the player around in a falling action, and teleport around the areas and the type of battle box), Cartoon Physics & Air Manipulation (Low Potency. Could make a self-sustaining tornado out of trash), Breaking the Fourth Wall (Aware of when Anomaly attempts to hack, directly winks towards the audience), Battlefield Removal (In the Dirty Hacker ending Sans removes you from the Undertale game making you unable to re-enter it), Clairvoyance & Information Analysis (Able to tell what the human's LOVE & EXP is at), Cosmic Awareness (Was aware of an anomaly messing with the time-space continuum, could tell how many times The Human died, and if the human has spared him before by the expression on their face, could tell from the look on the human' face that he already heard his speech beforehand), Gravity Manipulation (Makes the SOUL unable to float and can only jump around), Glyph Creation (Can create minature platforms), Energy Projection (With gaster blasters), Bone Manipulation (Has an assortment of bones in his attack), Telekinesis (Can throw your SOUL around), Teleportation (Has displayed it multiple times, can teleport during battle and the battle box along with your position), Karma Manipulation (Creates a status effect known as Karma that negates invincibility frames, and adds extra damage, based on your sins), Power Nullification (Able to lock his opponent in place so neither of them will be able to do anything).
Resistance to Extreme Colds (Lives in Snowdin), Extreme Heats (Casually sleeps while in Hotland)
Immortality (Ageless; Toriel will stay the same age forever as her child Asriel is dead thus she has no one for her SOUL power to flow into), Power Nullification (Nullified Flowey's magic attack), Fire Manipulation (Uses fire magic), Healing (Healed the human's wounds), Telekinesis (Moves her magic attack away from the human)
Weapon Mastery (Uses a trident and is skilled with it), Skilled in Hand to Hand Combat (Trained Undyne in hand-to-hand combat), Immortality (Ageless; Asgore will stay the same age forever as his child Asriel is dead and thus he has no one to transfer his SOUL power too), Acausality (Asgore remembers killing The Human after his resets), Fire Manipulation (Uses fire as a basis for many of his magic attacks), Power Nullification (Breaks the mercy option making the human incapable of doing mercy or fleeing the battle).
Resistance to Memory Manipulation (Asgore nods to the human when they note he's killed them before)
Weapon Mastery (Skilled with swords and spears), Regeneration (Low-Godly to Mid-Godly as Undyne the Undying. Regenerated her body which is attuned to her SOUL) Skilled in Hand to Hand Combat (Trained by Asgore in hand to hand and weapons), Weapon Creation (Creates spears), Energy Manipulation, Velocity Manipulation (Can turn the SOUL green making the opponent unable to move, this extends to their physical body as they can not flee from fights).
Resistance to Extreme Heats (Resisted the temperatures of the MTT Oven which is stated to heat over 9000 degrees Fahrenheit)
Body Control (Has extendable arms), Creation & Explosion Manipulation (Creates a large number of bombs, and mini versions of himself), Text Manipulation (Can turn his words into bombs), Energy Projection (Disco balls which fire lasers), Technology Manipulation, Hacking (Could out-hack even Alphys), Flight (Shown here), Inorganic Physiology, Cyborgization, Time Manipulation (Can rewind time with attacks), Electricity Manipulation (Can shoot electricity out of their fingers)
Enhanced Senses (Notices what The Annoying Dog does over the phone), Bone Manipulation (Uses bones for various attacks), Gravity Manipulation (Via turning your SOUL blue, it is no longer able to float around and is restricted by gravity).
Resistance to Extreme Colds (Lives in Snowdin)
Animal Manipulation (Can use spiders in battle), Web Manipulation (Uses webs to entrap your SOUL making it only able to move on the web strings), Summoning (Can summon her pet)
Undead Physiology, Immortality (Undead Immortality; Is a ghost), Non-Corporeal (As a ghost he is incorporeal), Invisibility (Can fade out), Acid Manipulation (Napstablook's tears are made of acid capable of damaging ghost), Telekinesis (Can control the direction of his tears), Text Manipulation (Creates text as one of his attacks basically stating he does not want to continue the fight), Limited Empathic Manipulation (Those who lie down with him feel like garbage)
Genius Intelligence, Cosmic Awareness (Shattered across all of space-time, can listen in on conversations while being outside of reality), Immortality (Life and Death Immunity; The concept of death no longer applies to him), Reality Separation (Reality Separation; Completely outside of Undertale reality), Paradox Existence (Concept and Non-Concept; Exists and doesn't exist at the same time, no longer bound by any concepts as he's completely outside of everything), Personal Nonexistence (Ayin Physiology; Gaster doesn't exist to the scale below even beings like Chara or Goner Kid. The mere act of acknowledging his existence or saying his name causes one to be erased or all of reality to reset. Even for the brief moments he can enter reality merely acknowledging him causes him to be completely erased), Acausality (Irregular Causality; The concept of causality doesn't apply to him as he is outside of it, he can appear at any point in time he wants and is seemingly unaffected by resets), Erasure & Nothingness Manipulation (Conceptual Erasure & Existence Erasure; Even acknowledging Gaster's existence or merely saying his name will cause you to be erased completely from existence), Spatial Manipulation (Created a new room between two points that were previously right next to each other, and erased it afterward), Passive Technology Manipulation (The Human's phone shuts down upon running into a follower)
Weapon Mastery (Uses an axe in the dark world), Elemental Manipulation (Rude Busters deals moderate "rude-elemental" damage), Healing & Resurrection (Via the various items she has, all healing items can revive party members), Consumption (Physical Consumption; Should be like Kris who can consume moss to heal), Sealing (Sealed Dark Fountain), Extended Blade Range & Distance Negation (Can attack a person via swinging their sword from meters away), Soul Manipulation & Essence Manipulation ( Could rip out their SOUL).
Resistance to Physical Attacks (All monsters bodies are attuned to their SOUL thus only attacks that can affect their SOUL can affect them), Soul Manipulation & Essence Manipulation (Can take hits to the SOUL)