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