Darkwood

To get the "Burn them all" ending, there must be roots growing under the floor of the protagonist's apartment. When you enter the apartment, you must first remove your coat. You then go into the living room to get the bedroom key from the wardrobe. When you're in the living room, move the furniture away from the wall. If you see roots, then you are able to get the burning ending. If you don't see roots on the floor of the living room after moving the furniture, you cannot get this ending and must restart the epilogue to have a chance to unlock the achievement.

At a minimum, to get the burning ending, you must first enter the basement of your apartment building. Wind your way around to a room containing a radio. Turn the radio on and keep switching the frequency until the Being starts talking through it, saying "Sleep." Then exit the basement.

This next step may or may not be optional, but it's quick, easy, and cool. Back on the ground floor, go north into the dark hallway where the wino/beggar is laid out on the floor. Try to open the metal door, walk away, wait for it to open and the person to yell at you, then go back up and look inside.

Now go upstairs and go north into the hallway. Past the scribbles, there's an opening in the wall. If you peer inside, you'll see weird stuff, and the lights will go out. That's a good sign.

Keep going north. Your apartment will be on your left. There are many apartments on the left side that you can enter, and they are all yours, but you must proceed far enough in the hallway that there are roots on the floors. At that point, enter your apartment. You can't exit, so you're committed now.

Remove your coat at the wardrobe. Go into the living room and get your bedroom key from the wardrobe. Now move all of the furniture from the walls and examine the roots. You must "Examine" all of them; simply looking and seeing that they're there doesn't cut it. Be sure to fold up the rug as well. Once you have exposed and examined all of the roots, go into the kitchen and grab the screwdriver from the cupboard. If that option isn't available, you haven't revealed and examined all of the roots. Just go back and keep at it. You can also interact with the items in the kitchen and bathroom just for flavor, they don't affect the achievement. If there aren't any roots on the living room floor, then you can't get this achievement and must restart the epilogue.

OK, now go back up to the living room and remove the flooring everywhere you can. Keep removing the flooring out into the hallway. Enter your bedroom and remove the flooring. Interact with the bed. Do everything you can with it except go to sleep (look closer, look under the bed, reach under the bed, move the bed). When you're back in top-down view, move the bed, and remove the last bit of flooring to expose a hole. Go in.

Make your way through the next area to the Being. You can examine the people on the way if you like. When you get to the Being, you can place your hand on it, but don't keep it there; withdraw it at the first prompt to do so. Now go to your left and look for a guy who isn't as dead or asleep as most of the other people. He's holding a flamethrower for some reason, which is very convenient for you. Take it from him and start flamethrowing all over the place. You will turn the whole area into a roaring inferno. You do need to find your way back out, though. When you get to the log where you crossed over, you'll lose control of the protagonist, and the game will end. Achievement unlocked.