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