Here is a little list how much you gain or lose karma if you do the following things:

Gain Karma

Car Extracts as PMC on Woods, Interchange and Customs

• 1st extract: +0.25
• 2nd extract: +0.13
• 3rd extract: +0.08
• 4th extract: +0.03

After the 5th car extract you get only +0.01 from now on. If you extracted 4 times on all 3 maps with the car you maximized your reputation for +1.47

Killing a Scav who killed a friendly Scav Player or AI Scav

• You get +0.1 reputation (Can be more if the "Bad" Scav killed more than one scav or scav boss/boss guards)

Killing a PMC as a Scav

• You get +0.01 reputation (Can be more if the PMC killed Scavs or a scav boss/boss guards)

Cooperative Extracts

• You get +0.2 reputation for using a cooperative extraction with a PMC + Scav like Scav Camp on Interchange or Scav Lands on Reserve. (It seems like only as a PMC you get reputation, as a scav you get item rewards from fence)

Lose Karma

Kill a Scav

• You lose -0.02 reputation for killing a AI Scav or player Scav.

Kill a Boss guard

• You lose -0.07 reputation for killing a Boss guard as a Scav.

Kill a Scav Boss

• You lose between -0.2 and -0.5 reputation for killing a Scav Boss as a Scav.

I hope this list will help some people!