20% increased Movement Speed if you've Killed Recently
10% reduced Damage taken while there are at least two Rare or Unique Enemies nearby
25% more Damage while there is at most one Rare or Unique Enemy nearby 
Opportunistic is a notable Ascendancy passive skill for the Assassin. It grants bonus movement speed if you've killed recently and causes your critical strikes to be unable to get reflected. It also grants more damage if there is one or no rare or unique enemies nearby or damage reduction if there are at least two rare or unique enemies nearby.