Thanks for the guide,
Heres some tips I found while playing through.
Slice and Dice – 10
Hit an enemy with the Slice and Dice knife attacks in the same turn
My "Boss" Character started with a knife and he was able to do this achievement straight away, I guess this maybe true for any of the other character who are able to wield it.
It's Getting Crowded Here – 15
Unlocked 15 gang members
Can also be done in multiplayer, if you buy all the characters on the manage team screen.
This maybe possible to do with the legendary weapons aswell, but they are quite expensive so I haven't tried it.
Scarface – 50
Won 25 multiplayer missions
If the other person quits out, or cancels the match at the "connecting to other player" notification, It will count as a win for yourself. you don't earn as much money, ($200 compared to the 700-800), but it makes it a lot faster to do