Kane & Lynch 2: Dog Days

Heres an easy way to get this achievement aswell as the 'Lightning Looter' achievement aswell.

Arcade
Subway

Now, once you start run down the stairs and into the hole in the wall, this will lead you to the room full of money. Kill the cops in here (Blindfiring works really well here) and loot as much money as you can. As soon as the enemy AI leave the hole in the wall you should head out, but if you look to the left before you leave the vault theres a pillar with a fire extinguisher, take the extinguisher. Once you leave the vault through the hole you will see many of the AI are huddled up together by the front of the train and some are up taking cover behind the pillars. What you do here is take cover by a pillar (preferably the further back one) throw the gas can into the enemies taking cover by the pillars and shoot it, this will clear all the enemies on the actual platform (hopefully, if not shoot the stragglers) now the remaining criminals will still be cowering in fear in front of the train, simply lean out of cover and blast them all to pieces. This shall hopefully kill them all. now loot the remaining money from their bodies and head up the stairs (the easiest is the right most stairs) once your on top of the stairs you will be in the lobby area. Blindfire the police around you and head to your right up the short stairs to the surface. Your now on the street, blindfire the cops and make a break for the van, get in and DING achievement unlocked.

Heres a short cliff note version incase you want a quick glance through after reading...

Arcade
Subway

* Enter vault and take as much money as possible

* Grab extinguisher on way out

* Throw the extinguisher into the criminals on top of the platform taking cover

* Blast the remaining ones by the train area

* Kill remaining stragglers (if there is any)

* Loot bodies

* Run up right most stairs and make an exit

* Run towards van and get in!

And as the previous poster stated, there is a total of $4'000'000 in every round.

I hope my guide helped you and thanks for reading

this is easier in arcade mode there is a max of $4million a round. just kill ur ai partners and pick up there money as well then just escape.

Here's an easy way to get this and also Lightning Looter if you're fast enough:

Play Arcade Mode on the Airport map. When you get to the room before the one with the plane and vans filled with loot, clear out everyone in your current room and take cover at the left edge of the door going into the loot filled room. Shoot the gas tank in the middle of the room. This clears away a lot of enemies and speeds things up. It's useful if you're going for the Lightning Looter achievement or are just trying to go fast, perhaps for the Love of Money achievement. When only a couple enemies remain, run into the room and enter the plane to collect the loot. Then, you should turn around to take out any of the remaining enemies possibly shooting at you. As soon as you collect all of the loot in the plane, get out and go for the loot in the vans. If you go fast enough, you will collect most of the loot before your AI team reaches it. It may take a couple tries to get the timing of this whole process correct. Once you evacuate by helicopter you'll get the achievement.