Monsters with a resistance over 99% are listed as "[element] immune" and will take NO damage from this type of attack.
Infinity's Conviction aura (Level 12) will reduce any non-immune enemy resistance by -85%, but ONLY works at 1/5 efficiency against immunes--so that's actually only -17% resist.
THEREFORE, if the enemy has higher than 117% total resist to an immunity, you will NOT be able to break its immunity with Infinity alone.
Once an immunity IS broken, however, all damage boosters start to passively work, i.e. +cold damage and -enemy cold resistance. Attacks such as these essentially INCREASE your elemental damage percentage and DECREASE enemies' resistances to that particular element.

Note: Location names are abbreviated, e.g. DoE = Den of Evil, or HoV = Halls of Vaught, etc.

UNBREAKABLES

ACT I
AREAS | MONSTERS
DoE,BM | Zombie - Zombie (I)
UPass,DW | Corrupt Rogue - Vile Rogue (II)
TH,P,MonGate | Corrupt Rogue - Dark Stalker (III)
OuterC,Barr | Corrupt Rogue - Black Rogue (IV)
GM,Hole | Gargantuan Beast - Brute (II)
OuterC | Gargantuan Beast - Yeti (III)
J,Cats1-3 | Gargoyle Trap - Gargoyle Trap
TH, MonGate | Skeleton Mage - Returned Cold Mage (I) -- debated in file, but not game
Cats3 | Vampire - The Banished (I)


ACT II
RW | Slinger - Slinger (I)
DH,HoD | Slinger - Spearcat (II)
S3 | Skeleton Mage - Burning Dead Cold Mage (III) -- debated in file, but not game
Harem,S3 | Skeleton Mage - Horror Cold Mage (IV)
VoS,CV Temple | Claw Viper - Claw Viper (II)
Tombs | Blunderbore - Gorebelly (II)
HoD, Tombs | Mummy Sarcophagus - Mummy Sarcophagus
CoM | Gargantuan Beast - Crusher (IV)
CoM | Sabre Cat - Hell Cat (IV)


ACT III
GM | Frog Demon - Bog Creature (II)
SF,GM,FJ,KB,UK | (ALL) Thorned Hulk (I-IV)
FJ,FDung | Fetish - Flayer [blowgun] (III)
KB | Zakarum Priest - Sexton (I)
Causeway,Trav | Zakarum Priest - Hierophant (III)
KB,UK | Zakarum Zealot - Faithful (II)
FTemp + Fanes | Claw Viper - Serpent Magus (V)
RTemp,DFane,FReq | Corrupt Rogue - Flesh Hunter (V)
DTemp,RFane,DReq | Corrupt Rogue Archer - Flesh Archer (V)
Rtemp,DFane,Freq,T | Vampire - Night Lord (III)
D1-2 | Vampire - Dark Lord (IV)
D3 | Vampire - Blood Lord (V)


ACT IV
OS,PoD,CoD,R | (ALL) Vile Mother & Child (I-III)
CS | Oblivion Knight - Oblivion Knight (III)


ACT V
BH,FH,AP | Slinger - Slinger (I)
FH,FT,AP | (ALL) Siege Beast (I-III)
GT,IC | Claw Viper - Pit Viper (IV)
CP,FR,GT,AW,IC | (ALL) Abominable (I-III)
CP,FR,GT,DC,AW | Skeleton Mage - Bone Cold Mage (II)
FR,GT | Reanimated Horde - Rot Walker (I)
AW | Reanimated Horde - Reanimated Horde (II)
HoA,HoV | Reanimated Horde - Prowling Dead (III)
WK1 | Vile Mother & Child - Flesh Spawner (I)
HoP | Vile Mother & Child - Grotesque (III)
WK1 | Vampire - Ghoul Lord (II)
ToD | Vampire - Dark Lord (IV)
InfPit | Vampire - Blood Lord (V)
InfPit,WK3 | Oblivion Knight - Oblivion Knight (III)
ToD | Skeleton Mage - Baal Cold Mage* (Death Mage)