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