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