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