Maid of Sker

At the end of the challenge, you get a numeric score and a letter grade. To get the A* grade, it seems you need 100,000 score. Based on my experience and a few other things I've read, to get the A* you cannot have died at all. The other two main criteria are your time and the number of enemies killed. I don't think tonics used, shots fired, accuracy, headshots, or anything else matter. You will, for sure, need to kill most of the enemies. A pacifist speedrun won't cut it.

I got it with 90 kills. That was nearly all of the enemies. I think I left 2 Elizabeths alive and maybe 1 or 2 out of the way ones, but no more than that. My time was 22:02 and my score was 102,100, so there wasn't a lot of room to spare. When I did a faster run (18:55) but only killed 69 enemies, my score was 95,290, which didn't make the grade.

NOTE: I had previously written that you cannot have died at all. I no longer believe this to be true, based on my A* rating of another challenge where I did die. As long as you get an adequate amount of kills in a decent amount of time, you should be good. The rule of thumb seems to be to keep it above 4 kills per minute, so 80+ kills in <=20 minutes ought to work.

To get your time down, you will have to do a fair amount of running, but you don't have to constantly run and rush. Always cycle and reload your weapons during the long runs and when in the ducts.