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