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