Here is the full list of all 50 Deadpool achievements.
Slap Wolverine a bunch of times
Playing with Deadpool's junk
Set the Dialog Volume slider to zero
Complete 'Taking a Chance'
Complete 'Job One'
Make a thousand pancakes
Be pretty
Get off your well-toned bottom
Score a combo higher than 40 before they lock the elevators
Get from the studio lobby to the boardroom without dying in 5 minutes
Take no damage on the waterslide
Defeat Arclight while taking no damage from her slam attacks
Use all three switches, defeat the two phasers, and chase after Vertigo within 60 seconds
Shoot everything from the Wheel of Insanity (Balloons and the Cow)
Play WTF is Cable
Kill 4 enemies in the Tower Plaza with stealth kills
Complete 'Genosha'
Get through Toxic River without falling into or touching the water and taking damage
Interact with all the ladies at the Shower Surprise Party room
Heh heh, good times
Get a stealth kill with every melee weapon in Sinister's Lair without being detected
Stealth Kill Sinister, in the Prison, with the Sword!
Complete 'Landed in Prison'
Get a high score at the Carnival
Find 11 treasure chests in the darkness of the Tombs
Beat 'Death, Baby' while wearing the pirate hat
Choose the patience option all the way through the line in the Carnival
Complete 'Death, Baby'
Collect all DP points and ammo in the bathroom
Shoot up the copier in the bridge offices
Complete the Breach in 10 seconds
Complete 'The Road to Victory'
Make it across the floating debris without falling
Complete 'Front Gates of EEEEEEEVIL!' from start to finish without dying
Score a combo of 75 or more while fighting up the stairs at the 'Front Gates of EEEEEEEVIL!'
Die 10 times in a row through the floating stairs
Complete 'Front Gates of EEEEEEEVIL!'
Complete 'Front Gates of EEEEEEEVIL!' from start to finish using only swords and pistols
Complete the game on Veteran difficulty
Complete the game on Ultra-Violence! difficulty
Complete 'Landed in Prison' without countering any attacks
In 'Genosha' reach the Fan Girl using only Hammers and Plasma Rifles
Collect 100 tacos
Purchase all Player Upgrades
Complete five Gold Challenges
Complete a Gold- or Silver-tier Challenge while countering at least 25 times
Combo an entire wave on any Gold-tier Challenge map
Kill a total of 15 enemies by holding cooked grenades
Upgrade all weapons to max
Bank a 300-hit combo