Snake's Revenge/Part 6

Last Building – First floor
Open the door to the north and take the elevator to go upstairs. Jennifer will contact you, telling you to hurry up. Then open the door on the right with Pass Card 6 to stock up on flares. Go south and open the door on the right with Pass Card 5. Force the hostage to speak and he will tell you that their leader is invulnerable. Go south again and then go back north, taking the passage in the middle. Go north and open the door with Pass Card 4 to fill up on grenades. Go south through the passage to the left and then to the left. Open the door with Pass Card 2 to free a prisoner. Then go south and reach the door on the right. Be careful though, in this screen there is a big trap in the floor, to avoid it always walk near the wall. Open the door with Pass Card 4 and inside you will find Pass Card 7. You will not be able to continue south due to the trap, so go back to the screen you entered. The path on the left is a dead end, so take the elevator and go up to the upper level.

Last Building – Second floor
Jennifer will call you again, informing you that the boss is on the top floor. Go left and move the square boulder with the power armor. Open the door with Pass Card 7 to stock up on plastic explosives, then head south. You will have to use the flare gun to light up the room. Be careful, as there are many traps in the floor on this screen. Reach the door on the left always staying close to the wall and open it with the Pass Card 4. Inside you will find a prisoner to free. However, walk close to the south wall, because there is a trap here too. By freeing the prisoner, your rank should rise to 6. Light up the room again, then reach the south wall, always staying close to the wall. Go right and, immediately after passing the row of thin crates, move north. Go right, staying against the south side of the crates. Also in the next screen you will have to use the flare gun and there are many traps. Reach the door on the right, always walking close to the north wall and open it with the Pass Card 2. Force the enemy to speak and go back. Go back to the north wall, then go straight south, staying just to the left of the chest in the middle of the room. Open the door on the right with Pass Card 5 (the path on the left is a dead end). You will enter an area without a floor, with moving platforms. Use the platforms to reach the door on the right wall and open it with Pass Card 5. In the next screen you can fill up on rations. Open the door on the right with Pass Card 2 and you can free a prisoner. However, walk close to the north wall, as here too there is a trap in the floor. Go back to the floorless area and this time reach the other exit to the south. Then open the door to the south with Pass Card 6. You will enter a very treacherous room, full of poisonous gas that will cause you to constantly lose energy and two orange squares blocking the south door, just like the ones you saw after defeating the first boss. Destroy them as quickly as possible with plastic explosives (it will take 7) or with your knife. Of course, you will have to sacrifice at least one ration to survive. Finally open the door with Pass Card 7. Go left. You can also ignore the door to the north. If you open it, with Pass Card 4, inside you will find a fake prisoner, who will explode when you touch him. Go left again and put on the boots to protect yourself from the spikes on the floor. Go north for two screens. There are traps in the walls here. Avoid the first by walking to the left and the second to the right. If you are hit, you will be poisoned, so hurry up and use the antidote. Open the door at the bottom with the Pass Card 7. Inside you will find the backpack and you can stock up on plastic explosives. Then go back to the screen with the door to the room with the fake prisoner. If you equip the X-ray viewer, you will notice a weak wall. Take it down with the plastic explosive and go north. Here too there are two weak walls, which can be knocked down with explosives. After destroying them, defeat the enemies and open the door to the north with Pass Card 7. The room seems empty, but you will hear whispers. Equip the bugging kit (this is the only point in the game where you need it) and you will learn that the only weak point of the boss are the soles of his feet. Then go left and follow the path to the end, being careful of the traps that can poison you. The best way to overcome them is to always walk alternately to the left and then to the right. Use the elevator at the end to go back downstairs.

Last Building – Back to the first floor
You should wear your bulletproof jacket, as there are many dangers in the next few screens. You will find yourself at the end of a long corridor. Quickly go south, avoiding the missiles fired by the statues. In the next two screens you will be attacked by an enemy with claymore mines, like the ones you saw on the train. Avoid them, or defeat them with gun shots. In the last screen to the south there are still the statues that launch missiles. Go right and ignore the first door to the north, as it contains a fake prisoner. Instead, open the door at the bottom with the Pass Card 6. You will enter another treacherous room with the poisonous gas and the squares blocking the door. Behave as in the previous one and open the door to the north with Pass Card 1. Go south and then left, ignoring the first path to the north. Take the second one and open the door on the left with Pass Card 7, to fill up on ammo and claymore mines. Go north and open the next door with the same Pass Card. You will find mines. Get as much of them as you can, as they are essential in the final battle. Then go north and take the elevator to go upstairs

Last Building – Third Floor
Go right. You'll get a call from Nick, who appears to be dying. Take the first path south and open the door on the left with Pass Card 4. You will find the final Pass Card, number 8 and Nick agonizing. Nick will tell you that Jennifer is a spy and that there is a life support system in the room where the boss is, then he will die. Exit and go back to the north (to the south you will inevitably be spotted by the enemies). Take the other path to the south and open the door on the right with the Pass Card 7. Inside you will find a smoke bomb. Go south again and then left. Open the door on the left with Pass Card 6 to fill up on guided missiles, which are essential to finish the game. After taking everything, go back to the elevator and go up to the top floor.

Last Building – Fourth Floor
Go right. In this screen you will be attacked by two robots. You can destroy them using your most powerful weapons, but it's best to just dodge their attacks. Go south. Here, too, you will be attacked by a robot. Avoid it and open the south door with Pass Card 8. Go left. The only door you can open here is the one on the left, with the Pass Card 3. In the next room you can only open the door on the right, with the Pass Card 4. Finally, open the door in the middle with the Pass Card 5 to finally reach the boss.

Boss fight - Big Boss
Higharolla Kockamamie will turn out to be none other than Big Boss, who survived the fight in Outer Heaven. He will first attack you by firing volleys of bullets. Move quickly and get behind the pillar on the right. In this position, Big Boss can't hit you, while you can easily attack him with your guided missiles.

But when you hit him with nine missiles, Big Boss will turn into a cyborg, declaring himself invulnerable. Thanks to the information in your possession, however, you will know how to defeat him. First, you'll need to lure him out of that room. Go south two screens and then right, using first Pass Card 5 on the middle door, then Pass Card 4 on the door on the right and finally Pass Card 3 on the door on the right wall. Meanwhile, Big Boss will chase you, passing through the doors that you cannot open. When you arrive here, select the mines from the weapons inventory. You should also equip the bulletproof jacket, because Big Boss attacks hurt a lot. Avoid hitting him in any way. The best way to defeat Big Boss is to stand next to him and keep releasing mines so that they end up directly under his feet, just like you might have done while fighting the tank. If your life energy starts running low, use a ration immediately. It is now useless to economize. Detonate about 20 mines under Big Boss's feet to defeat him.