Here's the list of all the achievements for the game. They are all really easy and you can have the 100% completion in one run if you know what to do.

Outcast
Complete the Bounty Hunter Guild Test





Revenge
Defeat Mueller in the Second Fight





The Fall of Icarus
Find Out the Truth About Aiden





True Prophecy
Complete the Game (wait for the cutscene after the credits)

Mercy
Hand Over the Rat Alive. When you fight a boss, you have two choice. Kill him with your blades / guns ou knock him out with the third arm. Here, you have to use your third arm to knock-him out (the orange bar has to decrease to 0).

It Will Hurt
Kill Basim Salamander Instead of Stunning. After the chase against Basim, he'll be trap and you have to knock him out to continue the story. But instead, just use your blades and kill him to get the trophy.
Alternative way: While you chase him, just use your gun to kill him (thx to Civanfan for the tip)

Lover of Weights
Carry All the Criminals in Your Arms. This applies only to the bosses, and there is only 4 of them you can miss (some are story related so I didn't include them). All you have to do is once they're are out / dead, to carry them to your ship and deliver them to the police. NEVER teleport a boss even if you have the choice (plus you'll get more money by delivering them personnaly). The 4 boss to carry are:
The Rat








Basim








The Cat








Mueller








(You can also carry Glitch and Genie but since they are mandatory to continue the game...)


Fastest Hand
Kill 100 Enemies with Pistols. Pretty easy, especially since bullets can kill severals enemies at the same time.


Head Hunter
Get a Reward for 30 Wanted Bandits
Pretty early in the game, you'll unlock the scanner which will give you the possibility to see enemis with bounty on their head. Kill them and teleport them x30 times. Scan every enemy to find them (there is more than 30 so it's ok if you miss some but it will also give you 500$ each time that you'll need to upgrade your character).
You can scan them once they are dead, bodies don't disappear.

Foresighted
Buy Ammo in the Store 25 Times
Not hard to do. Near the end of the game, you'll get 10 000$ to bring back a bad guy to the police. If you didn't unlock the trophy by this time, you could do it here (you can use your guns near the merchant to buy ammo until the trophy pop)

Bloodhound
Find and Open 50 Chests in the Game. Says it all. Chests are really really easy to find since most of them are on your road and there is at least 100 chests in the game so, again, it's ok if you miss some.