I follow a slightly different style when it comes to giving Traits to the souls of monsters. I have a total of (as of writing this) 18 different basic soul traits, 5 negative/fallen traits, and 8 different Effects. So SOULs themselves are a lot more complex in the Multiverses that I write.

I won't go into detail about all of the traits, instead, I'll provide you with their names and some information when needed, as well as characters who have said trait. The spectrum is also pictured above, with some of the modifiers to the side. It's incomplete and I will be updating it at some point.

I'll also make a full list of the characters' soul Traits at the bottom of this... well, minus a few whose would be spoilers.

Basic Soul Traits

Determination:
- You should know this one already
- Red in color
- Has the ability to save and reset only if someone who doesn't have more Determination isn't present in the AU
- Not safe in its raw form for monsters to bear
- Carried by all of the Chara and Frisk variants- including X-Chara

Fortitude:
- Red-orange in color
- Souls of fortitude often have trace amounts of Determination, which can grow to become dangerous only if the monster carrying it is close to death and determined to stay alive, i.e. Undyne the Undying.

Bravery:
- Hopefully you know this trait
- Orange in color
- Safe for monsters to bear, with no traces of Determination
- Bearers include Edge (UF!Paps), UT!Papyrus, and Syrah

Honor:
- Yellow-orange in color
- Bearers of this trait include Stretch, Blue, and Song
- Bearers of a soul of Honor can be relied upon to keep a promise, and will, rather like their close relation Justice, follow their own code. They are often willing to fight and even give their lives for others who believe in the same things they do.

Justice:
- Yellow in color
- It's likely that you already know this trait.
- This trait is carried in some form by the majority of Judges, although there are some exceptions
- Notable bearers of this trait include Stretch, Snow, and Quill
- The most powerful bearers of this trait can use it to unleash attacks of incredible power from those their opponent has killed. They need more power than the average monster soul can channel though, so most are unable to wield this ability. Even Dual Souls, such as Snow's, are barely able to handle it. Monsters who have absorbed a human soul of Justice will be able to use this ability.

Magnanimity (Forgiveness):
- Yellow-green in color
- Bearers of this trait are forgiving, but don't think that they're naive for doing so- they don't forget
- Bearers of this trait include Fynn (ST!Undyne)

Kindness:
- Green in color
- Hopefully you know this one
- Often are powerful healers and shielders
- Passive effects include an easier time creating monster food
- Carriers of this trait include Undyne, Quill, and Rhythm

Empathy:
- Blue-green in color
- Carriers of this trait include Dream, Quill, and Lune
- Bearers of this trait have high empathy for others
- It's found in the Toriels' of many AUs.

Patience:
- You know this trait, hopefully
- Cyan in color
- Carriers include Error, Nightmare, Stretch, and many others
- It's a relatively common trait, especially among those who can remember resets

Composure:
- A rather plain blue in color, darker than Patience but lighter than Integrity
- Carriers include Undyne (UT copy no.12 Undyne to be precise. She was the second to end up in ST, coming many, many years after Quill)

Integrity:
- Blue in color
- Bearers include Error, Blue, Lune, and Snow
- Common among Judges and their siblings

Morality:
- Blue-violet in color
- Bearers include Rhythm and Lust (yes, Lust.)
- Bearers of morality will stick to their morals, as you would expect

Perseverance:
- Violet in color
- Bearers include Syrah and Lust

Steadfastness:
- Red-violet in color
- Souls of Steadfastness often have trace amounts of Determination, which can grow to become dangerous only in extreme circumstances

Special Traits
Neutral:
- A dull gray in color
- An absence of defining traits, the Neutral soul can develop into Guidance, Love, or any number of things
- This is not a permanent Soul
- Bearers of this soul are often unable to feel, but they can relearn/learn how to do so with help, thereby gaining soul trait(s) of their own
- Fresh formerly had this soul, and if Ink had a soul (which he doesn't), it would be in this state

Guidance:
- A rare and powerful Soul that has trace amounts of Determination
- A trait that can only be learned by those whose souls were formerly in a Neutral state
- The only carrier of this trait in EitS is Fresh
- Closely related to Morality

Love:
- Either white or rainbow in color.
- A combination of all the basic traits in perfect balance
- Bearers include Azzy and the other Asriels
- Love is only found in incredibly pure and light souls
- The opposite of Hate

Hate:
- A dark soul, corrupted by LV or power
- Often develops from Wrath, Fear, or other darkened souls
- The antithesis of Love

Purity:
- Pale yellow in color, a pure and light trait
- Bearers of this trait are few and far between, with the only one in EitS being Dream
- Bearers of Purity see the world for what it is, but choose to believe in the good rather than the bad
- The opposite of Corruption, and close kin to Justice

Corruption:
- An extremely dark purple in color, almost black
- The only bearer of this trait in EitS is Nightmare
- Bearers of the trait of corruption can have difficultly seeing the truth, but with the light of a soul of Purity helping them, they can find their way back
- Once a bearer of corruption has seen the "light" they gain the ability to channel their darkness, using it as just another tool in their arsenal
- The opposite of Purity, and close kin to Perseverance

Trait Modifiers

Hope:
- A weaker light than love or purity, Hope tilts more towards one trait, and is a pale version of the trait's color
- It strengthens the non-attacking powers of that trait
- For example, Hope (Kindness) would be light green and have stronger healing magic

Wrath:
- A trait that can take over other traits, most commonly found in environments full of hatefulness and rage
- If the reason for the rage is lost or the carrier gives up, it will fade to Despair
- Carriers include Red, whose Wrath was formerly Kindness, and Edge, whose Wrath was formerly Empathy
- Error had Wrath- formerly Honor- at one point, but over the course of his time trapped in the Anti-Void, it faded to Despair

Despair:
- The third and final stage of a fallen trait, and the opposite of Hope, coming after the carrier of a fallen trait has given up on life and/or all hope
- The only known carrier of it in EitS is Error himself, as most carriers die- often by their own hand- before reaching this point

Fear:
- A darkened form of Bravery
- Colored a dark orange (unless created via a spell such as Bete Noir)

Vengeance:
- A darkened form of Justice
- Brown in color

Cruelty:
- A darkened form of Kindness
- Dusty green in color

Stagnation:
- A darkened form of Patience
- Dusty cyan in color

Deception:
- A darkened form of Integrity
- Dusty blue in color

Indifference:
- A darkened form of Perseverance
- Dusty violet in color

Special Soul Types
Negativity Guardian:
- Gains power from negative emotions
- Created from the combination of dark apples and the power of Chaos
- Apple-shaped soul

Positivity Guardian:
- Gains power from positive emotions
- Created from the combination of light apples and the power of Order
- Apple-shaped soul

Elemental:
- Souls of this variety tend to be extremely weak to the opposite of their own element
- In some cases there are multi-element elementals, they have more weaknesses than the average monster despite their power
- Examples of elementals include: Grillby, Eira, and Heats Flamesman
- Grillby and Heats are both Fire Elementals, while Eira was an Ice/Wind elemental
- Snow has partially inherited Eira's elemental powers, but can only use them while in her Frost Fury (Eira) form

Parasitic:
- An extremely rare soul type that has the ability to transfer itself to other bodies, but must feed upon soul energy to survive
- Fresh is a parasite, as I'm sure most of you know
- Unable to feel until they find someone who loves them for who they are and is willing to teach them how. The love can be romantic or platonic, it doesn't matter

Vessel:
- An empty soul
- The only souls able to such survive a terrible thing are souls of Love, and they lose their ability to feel love in exchange
- The most well-known being with a vessel soul is Flowey
- Can be cured using the powers of a full spectrum of human souls

Soul Effects

Glitched:
- Ranges in strength, from barely noticeable (Blue) to overwhelming (Error)
- Comes from the Anti-Void (blame Fate)
- Allows for the effected to hear the anons and readers, as well as causing them problems- such as blinding them- when they feel strong emotions.
- Can be destroyed/healed by beings of immense power, i.e. Destiny
- Will not effect souls of Determination.

Frosted:
- Causes the effected to take massive damage from fire of any kind.
- Found most commonly among ice elementals as a permanent effect.
- Used by some ice elementals as a weapon, will fade from the inflicted after the battle ends.

Characters' Soul Traits

UT!Asriel - Vessel (Love)

Azzy (Storyshift) - Love

Blackberry - Morality, Bravery, Wrath (Empathy)

Blue - Integrity, Patience, Hope (Honor) - Glitched

Chara (Storyshift) - Determination - Mage

Chronicle - Honor, Patience, Justice

Classic - Patience, Justice, Integrity

Cross - Vengeance, Deception, Determination - Dual Soul (X-Chara)

Dream - Purity, Honor, Hope (Empathy)

Dust - Vengeance, Cruelty, Wrath (Magnanimity)

Edge - Bravery, Honor, Wrath (Empathy)

Eira - Patience, Justice, Integrity - Elemental - Frosted

Error - Integrity, Patience, Despair (Honor) - Glitched

Fresh - Guidance - Parasitic

Fynn - Steadfastness, Magnanimity, Honor - Multi-soul

Geno - Patience, Justice, Integrity - Determination-infused

Hearts - Perseverance, Honor, Composure

Horror - Patience, Indifference, Cruelty

Ink - N/A

Killer - Deception, Cruelty, Wrath (Morality)

Lune - Empathy, Integrity, Hope (Magnanimity) - Multi-soul

Lust - Perseverance, Justice, Morality

Nightmare - Corruption, Patience, Perseverance

Outer - Justice, Integrity, Magnanimity

UT!Papyrus - Bravery, Integrity, Empathy

Quill - Kindness, Empathy, Justice

Raspberry - Bravery, Morality, Wrath (Empathy)

Red - Patience, Vengeance, Wrath (Kindness)

Rhythm - Kindness, Honor, Morality

Snow - Patience, Integrity, Hope (Justice) - Dual Soul - Frosted - Elemental

Song - Justice, Honor, Patience

Stella - Integrity, Justice, Patience

Stretch - Honor, Patience, Justice

Syrah - Bravery, Perseverance, Hope (Trust) - Multi-soul

Undyne - Fortitude, Kindness, Composure

If you have questions, feel free to ask.