As far as Japanese metallurgy was concerned, there was far more to it than mere layering.
Steel is merely iron with some carbon added. Overall hardness- or hardenability- was a simple matter of varying the amount of included carbon. More makes it harder, less makes it softer. (Also depending on how it was tempered.)
The layering is more than just folding. The easiest way to include carbon was to pound the bar out thin, stick it red-hot into a container of finely-pulverized charcoal, then fold it over upon itself, hammer it out flat and do it again.
The red-hot steel “absorbed” a small amount of the carbon from the charcoal, and the folding helped work it into the steel itself.
Few blades achieved the “millions” of layers- considering the thickness of the blade, anything over, say, several hundred layers basically formed a fairly homogenous mass.
The key here, that few know, is that the steels themselves were “layered” to vary the carbon content- and thus the hardenability- but the BLADE was also formed by layering.
In other words, a thin trip of “very” hard(enable) steel was backed by a slightly larger strip of much softer steel, and then these two were typically “sandwiched” between two “plates” of “medium” hardness steel.
(The “soft” steel obviously being itself layered relatively few times to include a small amount of carbon, the hard edge of course, being layered far more.)
So when the ingot were drawn out into a blade, there would be a very hard cutting edge, backed by a softer, more breakage-resistant spine, and reinforced on the flats with “plates” of a medium-hard steel.
Then we get into tempering- an art and subject all to itself. But briefly, the differences between the hard and soft steels was usually further blurred by careful, controlled quenching. The high-carbon edge was usually painted with a refractive clay paste (typically in a fancy pattern, which gives the trademark wavy temper line) so that when it’s quenched, the edge of the blade takes a few seconds longer to cool, which gives it a tough, springy, highly-breakage-resistant edge.
In what was considered the “mideval” times, new blades were occasionally tested on the bodies of prisoners- A good blade swung by an expert was supposed to cleave a body from right shoulder to left hip in one stroke.
As for the Samurai himself, I’d agree at, one-on-one, he’d be a formidable opponent for nearly any other warrior class within a dynasty or two either way from the era. And he’d be quite possibly the most formidable when unarmed.