Here is the full list of all 47 Hitman: Absolution achievements. It takes around 40-50 hours to unlock all of the achievements on Windows.
You left Lenny in the desert
You executed a point shooting with at least 3 kills
You completed 10 challenges
You played a contract made by a friend
You assassinated the facility leaders
You found your way through the mines
You circumvented Lenny's crew and secured Lenny
You re-gained your signature Silverballers
You questioned the bartender
You achieved Silent Assassin
You assassinated Wade
You assassinated Wade's men in Chinatown
You boarded the train and escaped the Chicago PD
You subdued a person
You contained a situation gone bad
You located the hotel room number 899
You successfully performed a lethal throw
You blended in and fooled someone
You escaped the attention of an enemy
You unlocked a technique
You remained undetected throughout a checkpoint
You fulfilled Birdie's contract and eliminated The King of Chinatown
You made a kill look like an accident
You hid a body
You infiltrated the mansion and assassinated Diana Burnwood
You completed 100 challenges
You completed 50 challenges
You performed 47 headshots using a sniper rifle
You have defeated Sanchez with your bare hands
You eliminated the Saints
You infiltrated the courthouse and accessed the jail
You caught up with Skurky
You visited Tommy the Tailor and acquired a new suit and gloves
You assassinated Dexter's assistant, Layla
You assassinated Blake Dexter
You eliminated Travis and fulfilled Diana's contract
You completed Hitman: Absolution™ as a professional
You collected all 20 play styles
You collected all evidence
You liked a contract
You earned 1 million contracts dollars
You bought an upgrade for a weapon
You completed the Creating Contracts Tutorial
You completed the Contract Basics Tutorial
You created a contract competition
You participated in a contract competition
You ran the benchmark mode to see how well your hardware performs