Damage Modifiers

Vulnerable to...

Phosphor/Fire
    Hallucinoid         170%

High Explosive
    Tentaculat          150%

Sonic
    Tasoth              120%
    Deep One            110%
    Gill Man            110%
    Calcinite           110%
    Tentaculat          110%

Stun(Freeze)
    Tasoth              110%
    Tentaculat          110%

Drill
    Lobsterman          200%
    Unarmored Soldier   160%
    Civilian            160%
    Aquatoid            160%
    Xarquid             145%
    Deep One            120%
    Gill Man            120%
    Plastic Aqua Armor  120%
    Ion Armor           110%
    Magnetic Ion Armor  110%
    Tentaculat          110%
    Triscene            110%

Electric Shock
    Unarmored Soldier   150%
    Civilian            150%
    Bio-Drone           120%
    Plastic Aqua Armor  110%

Resistant to...

Armor Piercing
    Bio-Drone          95%
    Deep One           90%
    Triscene           90%
    Plastic Aqua Armor 90%
    Ion Armor          80%
    Magnetic Ion Armor 80%
    Tasoth             80%
    Tentaculat         80%
    Hallucinoid        60%
    Lobsterman         20%

Phosphor/Fire
    Triscene           90%
    Deep One           90%
    Calcinite          90%
    Plastic Aqua Armor 80%
    Xarquid            60%
    Bio-Drone          40%
    Tasoth             40%
    Lobsterman         30%
    Ion Armor           0%
    Magnetic Ion Armor  0%

High Explosive
    Triscene           90%
    Tasoth             90%
    Ion Armor          80%
    Magnetic Ion Armor 80%
    Bio-Drone          80%
    Deep One           80%
    Hallucinoid        70%
    Xarquid            60%
    Lobsterman         30%

Gauss
    Deep One           90%
    Calcinite          90%
    Tentaculat         90%
    Plastic Aqua Armor 80%
    Hallucinoid        80%
    Triscene           80%
    Ion Armor          70%
    Magnetic Ion Armor 70%
    Tasoth             70%
    Xarquid            70%
    Bio-Drone          60%
    Lobsterman         30%

Sonic
    Ion Armor          90%
    Magnetic Ion Armor 90%
    Xarquid            90%
    Triscene           90%
    Lobsterman         50%

Stun(Freeze)
    Xarquid            90%
    Triscene           90%

Drill
    Tasoth             90%
    Bio-Drone          80%
    Calcinite          80%
    Hallucinoid        60%

Susceptible to...

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Ammo Type	Damage Modifier Category
Ammo Type	0	1	2	3	4	5	6	7	8	9	10	11	12	13
Armour Piercing	100	100	90	80	95	90	100	80	100	80	20	100	60	90
Incendiary	100	100	80	0	40	90	100	40	90	100	30	60	170	90
High-Explosive	100	100	100	80	80	80	100	90	100	150	30	60	70	90
Gauss	100	100	80	70	60	90	100	70	90	90	30	70	80	80
Sonic	100	100	100	90	100	110	110	120	110	110	50	90	100	90
Stun(Freeze)	100	100	100	100	100	100	100	110	100	110	110	90	100	90
Drill	100	160	120	110	80	120	120	90	80	110	200	145	60	110
Electric Shock	100	150	110	100	120	0	0	0	0	0	0	0	0	0

Please note that these are the actual numbers taken directly from the executable and are not from the Official Strategy Guide which is wrong.

Column	Unit Type(s)
0	Terrain.
1	Unarmored Soldiers, Civilians, Aquatoids, Zombies.
2	Plastic Aqua Armor.
3	Ion Armor and Magnetic Ion Armor.
4	Bio-Drone and possibly SWS's.
5	Deep One.
6	Gill Man.
7	Tasoth.
8	Calcinite.
9	Tentaculat.
10	Lobsterman.
11	Xarquid.
12	Hallucinoid.
13	Triscene.

Note: SWS damage modifiers are not shown in the Official Strategy Guide.