Here is the full list of all 36 Desperados III achievements.
Complete 5 of the Baron's Challenges.
Finish a mission on "Desperado" difficulty.
Jump from a tower into a cart of hay.
Kill 31 hidden Mimimi devs.
Interrupt an important healing procedure.
Kill 10 small animals in one mission.
Execute a plan with all five characters.
Kill all 3 golden chickens.
Find a patient for the dentist.
In the first part of the mission, burn 5 guards at once with oil traps.
Enjoy some cupcakes during a picnic.
Kill 200 guards using Cooper's double shot.
Defeat Frank.
Make guards follow Kate for 1,000 meters total.
Kill DeVitt.
Take care of DeVitt.
Kill 75 guards with Bianca.
Earn 90 badges.
Kill 5 guards at once with dynamite.
Kill 15 of the hidden Mimimi devs.
Meet Frank on a boat.
Find Wayne.
Decide the outcome of a duel.
Knock out your father.
Mind control 25 guards with Isabelle.
Kill 75 Long Coats.
Return the money to the bank.
Hide 750 bodies.
Make someone follow your footprints for 25 meters.
Snipe 50 guards with McCoy.
Blow up a bridge.
Kill 6 guards at once using only a single skill.
Kill 1,000 guards.
Kill 50 guards using the environment.
Hide 250 bodies.
Kill 500 guards.