Deadly Strike

Diablo II	Notation	Basic	Class	Skill	Item	Ally	Quest	Area	Monster	Tale

Crushing Blow	Enhanced	Minimum	Maximum	Adds Damage	Damage +	% Damage	to Demons
to Undead	Deadly Strike	Magic	Fire	Lightning	Cold	Poison
Skill Damage	ATD/ATLD	DR/MDR	Resistance	Maximum	Enemy Resist	Immune	Absorb	Sunder

Target overlay when critical damage is applied.

% Deadly Strike gives a chance to double physical attack damage when successful, even when barehanded. Overlay normally displayed when successful may be obscured by others (which gave rise to the myth that poison damage prevents it from being applied).

Since conversion of physical damage to another damage type occurs after it is applied, it can also double the converted damage of the following:
- Magic Arrow
- Fire Arrow
- Cold Arrow
- Lightning Bolt
- Fists of Fire
- Berserk (both the skill itself and its synergy to Concentrate and Frenzy)
It does not apply to the following:
- Impale
- Dragon Talon
- Dragon Tail
- Dragon Flight
- Sacrifice
- Smite
Percentages from multiple sources are summed, although when two weapons are equipped only that of the attacking weapon is added (that of the other weapon is ignored). >100% is redundant.
Mutually exclusive with Critical Strike and weapon Mastery or Claw Mastery critical strike: if one is successful then the others do not apply. Combined percentage chance of double physical attack damage is as follows:

Two sources	100 - (100 - DS)*(100 - CS)/100
Two sources	100 - (100 - DS)*(100 - MCS)/100
Three sources	100 - (100 - DS)(100 - CS)(100 - MCS)/10000 [1]

Non-player units like a Barbarian mercenary, Valkyrie and Iron Golem have 5% chance of applying critical damage, doubling all attack damage types. This is calculated independently of other sources, so there is a chance of applying quadruple physical damage. Combined % chance of double physical attack damage only is as follows:

Two sources	5+(0.9*DS)
Three sources	100 - 0.95(100 - DS)(100 - CS)/100 - 0.05(100 - (100 - DS)(100 - CS)/100)

% Chance of quadruple physical attack damage is as follows:

Two sources	0.05*DS
Three sources	0.05(100 - (100-DS)(100-CS)/100)

Percentage increase to average physical attack damage of a higher chance of critical damage is 100 * (higher chance - lower chance) / (100 + lower chance). For example, increasing Deadly Strike from 80% to 100% increases average physical attack damage from 180% to 200%, or by ~11% (100 * (100-80) / (100+80) ).

Helm

Value	Source	Min Rlvl	Ladder
(5-10)%	Blood helm	14	No
15%	Guillaume's Face Winged Helm	34	No

Amulet

Value	Source	Min Rlvl	Ladder
(0.375*lvl)%	Highlord's Wrath Amulet	65	No

Weapon

Value	Source	Min Rlvl	Ladder
20%	Lo Rune in socket	59	No
20%	Fortitude weapon	59	Yes
20%	Phoenix weapon	65	Yes
20%	Hand of Justice weapon	67	No

Melee weapon

Value	Source	Min Rlvl	Ladder
25%	Honor melee weapon	27	No
33%	Fury melee weapon	65	No

Axe

Value	Source	Min Rlvl	Ladder
20%	Grief axe	59	Yes
20%	Doom axe	67	No
35%	Butcher's Pupil Cleaver	39	No
(0.5*lvl)%	Death axe	55	Yes
50%	Razor's Edge Tomahawk	67	No
66%	Death Cleaver Berserker Axe	70	Yes

Club

Value	Source	Min Rlvl	Ladder
20%	Fleshrender Barbed Club	38	No

Dagger

Value	Source	Min Rlvl	Ladder
33%	Fleshripper Fanged Knife	68	No
35%	Heart Carver Rondel	36	No
40%	Deathbit Battle Dart	44	No
50%	Warshrike Winged Knife	75	Yes

Hammer

Value	Source	Min Rlvl	Ladder
20%	Doom hammer	67	No

Polearm

Value	Source	Min Rlvl	Ladder
20%	Destruction polearm	65	Yes
20%	Doom polearm	67	No
20%	Pride polearm	67	Yes
30%	Steelgoad Voulge	14	No
33%	The Reaper's Toll Thresher	75	Yes
55%	Pierre Tombale Couant Partizan	43	No
100%	The Grim Reaper War Scythe	29	No

Spear

Value	Source	Min Rlvl	Ladder
50%	Arioc's Needle Hyperion Spear	81	No

Staff

Value	Source	Min Rlvl	Ladder
25%	Arcanna's Deathwand War Staff	15	No

Sword

Value	Source	Min Rlvl	Ladder
20%	Grief sword	59	Yes
20%	Destruction sword	65	Yes
(0.5*lvl)%	Death sword	55	Yes
50%	Cleglaw's Tooth Long Sword	4	No
50%	Coldsteel Eye Cutlass	31	No
(1.5*lvl)%	Headstriker Battle Sword	39	No

Missile weapon

Value	Source	Min Rlvl	Ladder
20%	Brand missile weapon	65	Yes
20%	Ice missile weapon	65	Yes
25%	Leadcrow Light Crossbow	9	No
30%	Rogue's Bow Composite Bow	20	No
33%	Widowmaker Ward Bow	65	Yes
(lvl)%	Witchwild String Short Siege Bow	39	No

Throwing weapon

Value	Source	Min Rlvl	Ladder
40%	Deathbit Battle Dart	44	No
50%	Warshrike Winged Knife	75	Yes

Shield

Value	Source	Min Rlvl	Ladder
20%	Lance Guard Barbed Shield	35	No

Boots

Value	Source	Min Rlvl	Ladder
15%	Gore Rider War Boots	47	No

Reference

Special Magic Effects (Arreat Summit)
Question about "Critical Strike" on Insight (Technical Discussion)