This information no longer applies to the latest version of Diablo II. It remains here for archival use only.
First let's take a careful look at what exactly the descriptions of the damage-adding prefixes in the Chaos Sanctuary mean:
Merciless: 181%-200% damage.
Well, it does not mean 181%-200% extra damage. It means the weapon has 181%-200% damage of its normal value, or in effect 81%-100% extra damage.
Now let's move on to how a weapon's damage is calculated. While the formula should be simple, it's actually not. Here are 4 formulas the game uses to determine the damage of the weapon:
Maximum Damage Two Handed = Two Hand Damage + [(One Hand Damage + 1)*(Added up Damage Bonuses)] + (Extra Maximum Damage)
Maximum Damage One Handed = One Hand Damage + [(One Hand Damage + 1)*(Added up Damage Bonuses)] + (Extra Maximum Damage)
Minimum Damage Two Handed = Two Hand Damage + [(One Hand Damage + 1)*(Added up Damage Bonuses)] + (Extra Minimum Damage)
Minimum Damage One Handed = One Hand Damage + [(One Hand Damage + 1)*(Added up Damage Bonuses)] + (Extra Minimum Damage)
[ and ] mean rounding up
Let's take a careful look at it. Why does the game use one handed damage in its calculation of 2 handed damage? That is something Blizzard has to answer, but it definitely explains why Executioner Swords, with their normal 2 handed damage being higher then that of Bec-de-Corbins and many other 2 handed weapons, in reality doesn't even come close in their maximum possible 2-handed damage. Executioner swords have much smaller one-handed damage, while a Bec de Corbin's one-hand damage is very close to its 2-handed damage.
Another question you might ask is, "why do we add a 1 to the one-handed damage part in our calculations?" This seems to be how Blizzard solves its problem of not being able to use maximum/minimum values of its prefixes - so, in fact, the Merciless prefix can only add 99% damage at most, not 100% as stated. Now let's try to plug in some numbers for the maximum possible damages:
Maximum Damage Two Handed = Two Hand Damage + [(One Hand Damage + 1)*(1.98)] + 19
Maximum Damage One Handed = One Hand Damage + [(One Hand Damage + 1)*(1.98)] + 19
Minimum Damage Two Handed = Two Hand Damage + [(One Hand Damage + 1)*(1.98)] + 4
Minimum Damage One Handed = One Hand Damage + [(One Hand Damage + 1)*(1.98)] + 4
[ and ] mean rounding up
As you can see, we substituted the added up damage to a sum of maximum possible percent extra damage from the King's prefix (99%) and the Merciless prefix (99%) to get 198%. +19 and +4 are correspondingly the biggest +damage values you can get from "of slaughter" and "of performance" suffixes.
For Wands and Staves, the highest damage adding prefixes that can be used are Knight's and Massive, and only the "of gore" suffix can be used. Thus our formulas for them become:
Maximum Damage Two Handed = Two Hand Damage + [(One Hand Damage + 1)*(1.28)] + 9
Maximum Damage One Handed = One Hand Damage + [(One Hand Damage + 1)*(1.28)] + 9
Minimum Damage Two Handed = Two Hand Damage + [(One Hand Damage + 1)*(1.28)] + 4
Minimum Damage One Handed = One Hand Damage + [(One Hand Damage + 1)*(1.28)] + 4
[ and ] mean rounding up
Also, please note that the values that are used for added damage are separate for Maximum and Minimum damage calculations. Thus, you can have a Lance with maximum possible damage, but its minimum damage can be far from the best.
This table lists the maximum possible damage values for all weapons in the game. The values in this table for wands and staves are written with consideration that staves/wands cannot accept any damage prefixes higher then knights/massive, and suffixes no bigger then "of gore," which they considered as +9 to max damage.
The light brown celled values mean that those values are not possible/not used by the game to calculate damage (as with bows). In other words, since there is no 2-handed damage on Hand Axes, the cell is shown in light brown.