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