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