Here is the full list of all 36 Wild Frontera achievements.
Collect 4,751 gold
Spare the life of 100 bandits
Complete all Stages in MOST WANTED difficulty
Complete a stage wihtout dying
Resurrect a friend in a co-op game
Buy a Custom Quality shotgun
Buy a Custom Quality Revolver
Buy a Custom Quality rifle
Find all the cards
Buy all the character upgrades
Save 100 damsels
Destroy all the portals in less than 5 seconds
Kill the Bufferatops ghost first
Kill the sow while 5 piglets are alive
Do not let more than one sniper alive at the same time
Reach a 5 star wanted level in co-op freeroam. "Now that's hard", Bestio.
Stand on the last platform at the end of the encounter
Kill Poncho Bob with 3 turrets up
Kill all the Banditos running from Poncho Bob
kill all the pigs before they flee near Pueblo del Norte
Complete all Stages in normal or easy difficulty
Complete Stage VIII in any difficulty
Complete Stage VII in any difficulty
Kill the Executioner with a punch as final blow
Complete Stage VI in any difficulty
Kill the BergMeister with explosives only
Kill 1000 enemies
Complete Stage V in any difficulty
Activate all the detonators in less than two minutes
Complete Stage IV in any difficulty
Kill 8 minions in less than 20 sec while fighting the mysterious masked man
Complete Stage III in any difficulty
Kill Bufferatops in less than 1min 30 sec
Complete Stage II in any difficulty
Do not let a single suicidal bandit explode while fighting SteelNugget
Complete Stage I in any difficulty