The prefix of a legendary-type armors dropped by Legendary Enemies determine its bonus effects. See the list below for the prefix's effects.
Almost Unbreakable | Quadruples durability (Power Armor only). |
Assassin's | Reduces damage from humans by 15%. |
Bolstering | Grants increasing energy and damage resistance the lower your Health (up to +35). |
Cavalier's | Reduces damage while blocking or sprinting by 15%. |
Chameleon | Enemies have a harder time detecting you while you're sneaking and not moving. |
Cunning | +1 Agility and +1 Perception |
Duelist's | 10% chance to disarm melee attacker on hit. |
Exterminator's | Reduces damage from Mirelurks and bugs by 15%. |
Fortifying | +1 Strength and +1 Endurance |
Freefall | Prevents falling damage.(Needs to be present on both equipped leg armors) |
Ghoul slayer's | Reduces damage from Ghouls by 15%. |
Hunter's | Reduces damage from animals by 15%. |
Low Weight | Low carry weight. |
Lucky | +2 Luck. |
Martyr's | Temporarily slows time down during Combat when you are at 20% or less Health. |
Mutant Slayer's | Reduces damage from Super Mutants by 15%. |
Piezonucleic Lining | Radiation exposure increases Action Point refresh speed. |
Poisoner's | +25 poison resistance. |
Powered | Increases Action Point refresh speed. |
Punishing | Reflects 10% of melee damage back on attacker. |
Safecracker's | Increases size of sweet spot while picking locks. |
Sharp | +1 Charisma and +1 Intelligence. |
Sprinter's | Increases movement speed by 10%. |
Titan's / Sentinel's | Reduces damage while standing and not moving by 15%. |
Troubleshooter's | Reduces damage from robots by 15%. |
VATS Enhanced | 10% reduction in Action Point cost in V.A.T.S. |
Source: Fallout Wikia