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