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