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