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