Resident Evil Revelations 2

An easy way to boost this is to go to the place in Barry's campaign you see in the video. As you descended and can grab the bottle throw it at the two Revenants in front of you. You can quit to the main menu and repeat the process as often as you need it. In the video attached I show the process.

After you knock down the gate with the log pile in the lumber yard there is an infinite spawn of revenants that appear, two at a time. Just make sure you don't go close to the gate or a cutscene will appear and mission over. just keep killing them until the achievement pops, no reloading checkpoints required.

Also, at the end of claires campaign there is another infinite spawn of afflicted that appear. After you place the cog in the wall, remove one board with the crowbar and bam, infinite spawn. Two at a time as well. I got the knife achievement, 100 afflicted achievement, crowbar achievement, flashlight achievement, follow up achievement, physical attack achievement in about 20 minutes doing this.