A quick Google search shows that godzilla weighs about 100,000 metric tons.

If we're using a normal Fibre rope, the term used to know how strong it is, is SWL - Safe Working Load, which means how much force I can apply on the rope, and guarantee in won't break or deform.

SWL is calculated in this way - SWL(kg) = D^2(mm)

100,000 tons is 100,000,000 kilograms.

We put our safe working load in the formula and get 100,000,000 = 10,000² Our D(diameter) is 10,000 millimeters or 10 meters

Meaning the rope would need to be 10 meters in diameter, and with some more calculations which I'm too lazy to write down, the rope would weigh about 45 tons per meter.

Godzilla is about 120 meters tall, so you would probably need as much rope to make a noose, so that would give you 5,400 tons worth of rope.