It's probably not the absolute cap as I've likely missed some effects, but if my calculations are right I can get to
99.28% cold absorption with this breakdown.
Note: I'm not entirely sure that the LGS bonuses are indeed Equipment and Exceptional for tier 2 and 3 respectively. That's purely based on the character planner (the wiki doesn't specify their types).
The build is 6 Favored Soul / 13 Druid / 1 Monk.
3 - Past Life: Arcane Sphere: Ancient Knowledge
3 - Past Life: Arcane Sphere: Arcane Alacrity
3 - Past Life: Arcane Sphere: Eclipse Power
3 - Past Life: Arcane Sphere: Enchant Weapon
3 - Past Life: Arcane Sphere: Energy Criticals
30 - Past Life: Divine Sphere: Block Energy
15 - Unyielding Sentinel: Mantle of the Sentinel
25 - Grandmaster of Flowers: Flow of Water
25 - The Flow of Water + Ocean Stance
10 - Energy Resistance: Cold (Favored Soul)
15 - Primal Avatar: Weathering the Elements
15 - Shrine to the Devourer IV
65 - Wild Shape: Water Elemental
1 - Deck Curse: Curse of Divine Fortune
38 - Cannith Crafted Prefix: Cold Absorption
2 - Curse of Major Masterwork (On Cannith Item)
30 - Greensteel Weapon Tier 2: +30 Equipment bonus to Cold Absorption
35 - Greensteel Weapon Tier 3: +35 Exceptional bonus to Cold Absorption
5 - Filigree 1 (Weapon): Frozen Wanderer: Cold Absorption
5 - Filigree 2 (Weapon): Dragonsoul: Cold Absorption
5 - Filigree 3 (Weapon): Snowpeak's Gifts: +5% Cold Absorption
5 - Filigree 4 (Weapon): Nystul's Mystical Defence: Cold Absorption
5 - Filigree 1 (Artifact): Frozen Wanderer: Cold Absorption
5 - Filigree 2 (Artifact): Nystul's Mystical Defence: Cold Absorption
5 - Filigree 3 (Artifact): Dragonsoul: Cold Absorption
5 - Filigree 4 (Artifact): Snowpeak's Gifts: +5% Cold Absorption
25 - Amaunator's Flame
That gives us a standing
99.11%
You can then cast Greater Inflame on yourself for another 15% for 30 seconds every 1 minute.
And if you had a level 18 Dragon Lord friend with a White Dragon Soul then you could get another 5% from his aura.
Which gets us to the total of
99.28%
It would be a complete gimp build, but we're just trying to see what is possible
If what Lominal says is true (that rng loot can have 40%) then you can add another 2% as I'm basing my number on the max possible through cannith crafting which is 38%.
There's an enhancement for Winter Wolf that gives 30% cold absorption, however it doesn't list its type and the planner puts it as Enchantment so it doesn't stack with Fire Shield.
Combined with Fire Shield this would give you more raw cold absorption than Water Elemental, but due to how multiplicative calculations work it ends up the same.
It's also possible that the heroic greensteel absorption effects stack with the legendary ones which would potentially mean that it's better to dual-wield a HGS with a LGS weapon. This would forego the weapon filigrees, but would be a nice increase overall. They likely share the bonus types, though, so this is just a wild theory. If only tooltips actually showed the bonus types, right?
Also there's the feat "Shield Deflection" which would give you a 40% chance to completely negate any elemental damage taken. That's slightly different, but worth noting.
Out of all the elements Cold can reach the highest at
99.28% because Amaunator's Flame is pretty big.
Fire is the second highest at
99.22%. This is because it has the most filigrees and you can get an extra 5% from Exalted Angel. Due to the fact that it doesn't need Amaunator it can be a Warforged which enables the Guardian of the Gates set on monk.
Electric is next at
99.10% as it has fewer filigrees. You have to go Ranger/Wizard/Monk for this.
It slight makes up for the loss of elemental form with the tempest imbue giving 30% and Palemaster 15% from its core. It can also use the Guardians of the Gates set.
Acid is worst of the elements at
98.71%. There are simply much fewer filigrees for it and no major increase from enhancements or forms. It can only get 15% from Blightcaster. This too can use the Guardians of the Gates set.
Disclaimer:
- The numbers might not be the absolute maximum as it's possible I missed stuff.
- All of the values used are based off the wiki. They might be differet in game.
- Things might not stack like I assume (most effects don't list a type)
- It's also possible that the game calculates the values differently than I did. For example: there is the same amount of raw Fire and Electric absorption but due to how large numbers are worth more when doing multiplicative calculations Fire wins out with Fire Elemental.
Maybe the game compensates for this.