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