+40% to Critical Strike Multiplier against Enemies that are on Full Life
100% more Critical Strike Chance against Enemies that are on Full Life
Critical Strikes have Culling Strike
100% more Critical Strike Chance against Enemies that are on Low Life 
Ambush and Assassinate is a notable Ascendancy passive skill for the Assassin that grants more critical strike chance against enemies on full or low life, added critical strike multiplier against enemies at full life, and more damage with hits and ailments against enemies at low life. It also grants culling strike to critical strikes.