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