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