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