Resident Evil 8 - Knife-only Speedrun Guide

0:01 - Finish the game at least once to unlock Extra Shop and unlock Karambit Knife there before you load your Clear game save. Make sure to load your clear game save and play on Casual for an easy run
0:17 - Prologue
1:27 - Village 1st Visit
21:33 - Buy Karambit Knife for 100 Lei if you didn't carry it from your previous playthrough
22:10 - Castle Dimitrescu
27:10 - First Sister fight
29:40 - 4 Statues Puzzle
35:18 - Second Sister fight
35:50 - 5 Bells Room (You need to shoot some bells with your gun here)
40:00 - Third Sister fight (You can use the Pipe Bomb to blow up the wall here)
41:40 - Mask Puzzle and Lady Dimitrescu fight
47:41 - Vilage 2nd Visit
50:25 - Lock Puzzle for Jack Handle
57:18 - House Beneviento
1:08:20 - House Beneviento Boss
1:13:19 - Village 3rd Visit
1:14:30 - Moreau Section
1:18:55 - You can use your gun here to shoot the platform, no way around it
1:23:57 - Flood Gate Puzzle
1:24:54 - Moreau Boss fight
1:28:50 - Village 4th Visit
1:29:46 - Stronhold
1:34:10 - Stronhold boss
1:38:51 - Factory
1:51:47 - Big hall (here you need to shoot 4 lights with your gun to proceed)
1:53:56 - Ventilator Room (here you need to use your gun to survive the propeller)
1:58:52 - Sturm Boss
2:02:05 - Heisenberg Boss
2:06:20 - Chris Section
2:10:38 - Chris Boss
2:19:40 - Final Boss (I used 2 Healing Potions here, since I never used any so far, so under 4 are allowed)

Detailed Guide & Tips

I will cover Knife Only playthrough, less than 3 Hours Speedrun, less than 4 Healing Items & Spending less than 10,000 Lei (money) in this topic. You can do them all in your 2nd run, which will prepare you real good for the 3rd and final run. Play on EASY mode, otherwise good luck :)

I recommend unlocking Karambit Knife from the Extra Content Shop before you start, then buying it from the Duke (merchant) for 200 Lei. This knife is way stronger than the default one, so you might want to invest in it.

You must use Knife in all occassions, except when you need to shoot some object to progress + SOME of the boss battles (be very careful!). I will try and note all of this in the next topic. Also, loot all you can to collect as much money as you can, but be careful not to spend moer than 10,000 Lei during this run.

You can keep track if you made a mistake via the Challenge Menu. From the Pause Menu go to Challenge -> find the Knives Out challenge. If it shows 0, you are good to go! I recommend keeping mutliple save files and checking this every now and then. If you mess up, load the save when the counter is 0 and continue from there.

Like mentioned, on some parts you can use your weapons as you will have to, so I will note those occasions bellow, plus boss fights and strategies:

• Castle Dimitrescu, Atelier Room with 5 Bells - You need to shoot the bells with your weapon, which also includes breaking the roof window and moving the chandelier. 
• Castle Dimitrescu, Armory - One of the sisters here is beatable only when you destroy the well with the explosive. This means you can use the Pipe Bomb to do so, then continue with your Knife.
• Lady Dimitrescu Boss - Well, Knife her in the head, you must aim to get close when she lands. You need to kill her using only your Knife.
• Moreau Reservoir Area - After Moreau transforms into a fish, you will have to traverse this water area and bring down the paths by destroying yellow objects. Only 1 of those is not reachable without a gun.
• Moreau Boss - Like the Dimitrescu fight, get close and Knife in the head. You can't use guns here.
• Urias Boss in Stronghold - You can use only Knife here. Circle around and cut him up.
• Heisenberg’s Factory, Grinder Area - In room with the spinning Grinder Blade at the top, you will need to stop it by using your gun to shoot the orange lights. Ony shooting at them is allowed.
• Heisenberg’s Factory, Ventilation Shaft - When a Ventilator tries to suck you in, use your gun to shoot the orange light.
• Sturm Boss - Just let him run into a wall, go behind him and cut the glowing orb.
• Heisenberg Boss - You can use the machine and its weapons in the first phase. When you land on foot, it's only Knife time! Aim for the head, block and be careful. Last phase in the air is automatically scripted and you can shoot from the machine.
• Section with Chris - Run until you get to the Laser Pointer section. You must use the Laser Pointer 3 times in a row on the house to destroy it. Just ignore the enemies when Laser is charging. 
• Boss Fight in Chris Section with the mace-wielding creature. Cut his right leg and left arm. This will take a while, just be patient. You can know if you are doing the right thing by the blood that comes out after a succesful hit.
• Miranda Boss Fight - Melee all the way, block when she is in spider and flying form. When the animated part starts and she throws you on the ground, shoot the energy ball to make it explode, then switch back to your knife immediately after and finish her off.

All other parts of the game are not exceptions and you MUST use only melee attacks.