Underpass

Run through the health-draining hall in the Underpass as quickly as possible, ignoring all enemies. Do not heal until after this section, as it will not kill you.

Consider using the Shotgun and kicking for fighting kills against Numb Bodies (enemies that attack with lunges) in this area, isolating them whenever possible.

Be aware that more Numb Bodies will spawn after leaving the Wine Bottle hallway. Be very quick to run to the other wall and left hook around the large one to avoid its aggressive lunge.

Consider leaving the spawned Numb Bodies alone afterwards, unless you can isolate them.

In the sewers, jump in the water and kill the two large Numb Bodies with the Steel Pipe's downward swing. They cannot hit you from above while you swing from the water.

In the next area, lure the Numb Bodies out one by one, getting Shotgun fighting kills with kicks if possible.

Sprint through the next area with Pendulums (obstacles that swing back and forth), and do the same for every other area containing them.

In the sewer monster room, examine any part of the water and answer honestly (No, No, Yes) to get the Gold Pipe and Silver Pipe. You should now have all 5 Extra Weapons needed.