When you first play the
Clash in the Clouds DLC you'll have to pick up the first 4 vigors on the table to your left |FREE SAMPLES|, then when playing some of the waves you'll have to save up money to buy the rest of the Vigors. Once you start to combo on a kill you'll see what you combo pop up in white and how much money you've earned.
Total of
8 different combination moves are:
• Possession and Shock Jockey
• Possession and Devil's Kiss
• Devil's Kiss and Charge
• Murder of Crows and Devil's Kiss
• Murder of Crows and Shock Jockey
• Bucking Bronco and Devil's Kiss
• Bucking Bronco and Charge
• Undertow and Shock JockeyLoad up Raven's Dome for the last couple of kills you need done and keep doing Wave 1 or Wave 2 if needed.
For
Possession + Shock Jockey you'll have to Possess the enemy first then shock them repeatedly until the Possessed enemy gets a kill while being shocked. The Possessed Enemy HAS TO GET THE KILL, NOT killing the enemy with Possession and Shock Jockey.
For
Possession + Devil's Kiss you'll have to Possess the enemy first then Devil's Kiss setting them on fire, the Possed enemy HAS to get the kill while being on Fire. This is a bit tricky since you could kill the Possessed Person with Fire Damage or it delays the kill. The Possessed person has to get the kill.
You might wanna upgrade the vigors or salt infusion or at least damage the enemies then use it. It's a cumulative achievement so you can come back to it or do it on any waves. (Also what helped me was putting a check mark or opening a word document on the ones I already did.)
Keep trying every combination again if it didn't unlock. I strongly suggest writing them down or a word document to keep track and to tally off which ones are done. If for some reason it's not unlocking come back to it once your done with ALL the achievements and delete your save and start a new save make sure you cancel the upload save when you start the game. But I really recommend you do this if it's your last hope on 100% this game.