Minimum difficulty: I AM DEATH INCARNATE!
Achievement for Gold Medal: Research centre combat master

Minimum difficulty: I AM DEATH INCARNATE!
Achievement for Gold Medal: Prison docks combat master

Minimum difficulty: I AM DEATH INCARNATE!
Achievement for Gold Medal: Keep foyer combat master

Minimum difficulty: I AM DEATH INCARNATE!
Achievement for Gold Medal: Cable car platform combat master

Minimum difficulty: I AM DEATH INCARNATE!
Achievement for Gold Medal: Caves combat master

Notes

4:05 The spawn of those two enemies can be triggered by using the turret.

6:15 Apparently, the enemies spawn once you enter the elevator, so DO NOT press the button immediately, because the level will end.

Minimum difficulty: I AM DEATH INCARNATE!
Achievement for Gold Medal: Pradeborn bridge combat master

Minimum difficulty: I AM DEATH INCARNATE!
Achievement for Gold Medal: Wulfburg square combat master

Notes

I decided to pick the slower but safer way to earn this Gold Medal.

Try to remain stealthy until you climb the tower and after that wait for opportunities to headshoot the enemies. Be careful not to shoot the commanders as they are the ones who raise the alarm - so save them for last.

Minimum difficulty: I AM DEATH INCARNATE!
Achievement for Gold Medal: Workshop combat master

Important: To unlock this level, simply choose to save Kessler in Chapter 6 - Ruins.

Minimum difficulty: I AM DEATH INCARNATE!
Achievement for Gold Medal: Bathhouse combat master

Important: To unlock this level, simply choose to save Annette in Chapter 6 - Ruins.

Minimum difficulty: I AM DEATH INCARNATE!
Achievement for Gold Medal: Graveyard combat master

Notes

After you clear the first area of enemies, do NOT attempt to power down the door as this will end the level with your score far from the one required for Gold Medal. Instead take the path shown at 2:35 and clear that area as well. The enemies there will be your opportunity to reach the desired score.