Killabilly
Killabilly will start throwing cars at you. Hit the cars with the chainsaw as they pass. When a car passes, you'll be prompted to hit it. If you hit every car that you are prompted to hit in both this section and the next, you will get an achievement. For right now, hit the four cars and then dash across the gap. When you get stopped by a group of zombies, you'll find two named zombies David and Marie during a second playthrough on hard. Continue through them towards Killabilly.
When you get to the next gap, hit three more cars to create another ramp. When you've successfully done that, you will have to dash across and then keep grabbing the gas cans to move along. If you see a ramp to your right, try to hit it so that you land on a school bus for a Golden Lollipop on normal. A building will start to fall and you'll have to get past it before it lands on you. Keep your eyes to the left for an arrow. You want to go onto that side street. When you get there, the achievement should unlock for the cars you hit earlier.
*Achievement: Aced Auto-shop Class
There will be a group of zombies on this street. Kill them all using the barrels and then go shopping if you'd like. Head into the next street and Killabilly will start shooting laser beams out of his eyes. Make our way up the street using debris for cover. In a couple of instances, you may need to wait for him to destroy a piece of debris before you can get through. Keep pushing up until you get behind an overturned truck and zombies appear. There will be 10 zombies and as long as you stay close to the truck, you'll be safe from the lasers. Just take these out like any other zombies. Eventually, the truck will explode and you'll have to dodge the laser (no prompt). Dodge and start dashing towards Killabilly again.
Killabilly
The first stage of the fight is actually pretty simple. You can move left and right by pushing left and right (she'll use the chainsaw to control him). You want to shoot him in the eyes. When he opens his mouth, he'll shoot a red zombie at you that you can't kill. Your only option is to dodge it. Dodge and then keep shooting. If you push too far right, he'll try and flick you for which you'll be prompted to dodge. If you run out of ammo, flying zombies will appear and fly up close to you. Each one killed will give you an additional 12 shots. Keep shooting his eyes.
You'll find yourself on the ground now and have to fight regular zombies as you fight him. It's important that you don't kill him too quickly. You want to cut off his fingers when he puts his hands down. Eventually, they will grow back. You want to cut off 20 of them for an achievement. Watch out when he opens his hands palm up or his tongue rolls out quickly because he's going to throw a car or two full of zombies at you. You'll also have to watch out for exploding trucks that drive around and other flying vehicles.
*Achievement: Fingered
Kill the zombies he throws at you so that he'll come closer to the ground. Whenever you can, get close in to his arms and start hacking at them. It might seem like this fight is taking an unusually long time but that's just how this fight goes. There's not a whole lot you can do about that.
Once inside, cut your way through the structures in front of you. After you get past them, you'll have to dodge and cut a few more things as prompted. Doing so will end the game. If you have saved all of the students, you'll get the good ending. If not, you'll get the bad ending.
