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