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