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