Shadow Warrior

If you are like me, and you purchased the sticky bomb upgrade for the crossbow shortly after acquiring it, (I had $4500 directly after I picked it up, go figure), then there is a place you can get this at the beginning of Ch. 4. After you progress far enough to break the red seal, you should emerge on the street. If you progress forward, (turn left after exiting the door), several Yakuza should try to kill you. Kill them however you wish, but save the bombs. THEN SAVE THE GAME.

After they are dead, back up until you stand adjacent to the blue truck in the road and wait. At this point, 9-10 regular claw demons should run at you from where the Yakuza were up the road. When one gets close, tag him with the sticky and detonate. This should kill him and set several of his friends on fire , (but not kill them). If you react quickly and kill those aflame with the sticky too, you can get credit toward the "Merciful" achievement.

Always fire stickies one at a time. I had a tendency to miss if I got overzealous. Fire. Detonate. Repeat. You will know you are correct, if you see the little "Detonated" moniker appear on screen. Once the 9-10 demons are dead, reload the save I told you to make and repeat. (Killing the shield demons that appear afterward is too difficult and requires more than one sticky). Even with only 9-10, I managed it in 20 minutes.

Cheers

(On a side note, you do not actually have to penetrate the demons with the bolt to count the kill. As long as the sticky kills them, say it lands on the ground near them, and you get the moniker, then you are fine.)

Hey all, this video shows how to get all of the kill achievements. Hope it helps with them.