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