Although stealth is an objective for the Hacker, it's not necessary. I normally defeat the thugs so I can hack in peace (and still get the badge.)
For the thief, the laser challenge is a little easier if the camera is tilted to a more "top down" view.
The Ninja Monkey badge is made easier with AoEs, naturally.
For Man's Best Friend, the players should defeat the two-or-three brown dogs before attacking Frank. Once the brown dogs are defeated, then the players can focus on the badge.