Most underrated composer of 20th Century?

The ancient strategy of the evil one is to cloak evil in the guise of banality.

A person, or a society, is either getting better or worse.
Not all rock is bad or evil per se, but its no help which
in the end is evil. You don't get to"hell' by jumping off a cliff but by sliding down a slope.
True, there are shades of gray , but the important stuff tends toward black and white.

Its true there is less hypocrisy now than before rock,which may be a good thing in personal relations but is not necessarily a good thing for society in general.
Hypocrisy is the tribute vice plays to virtue, permission to feel guilt-free is no advance.

"Those not alive and of the age of reason before _____ arose have no idea of the great harm _____ has done to society." - A great number of idiots throughout history

"All those whose mind entitles themselves,and whose main entitle is themselves,shall feel the wrath of my bombast!" - Mark E. Smith (rock musician)

I am a big believer in the concept of Yin and Yang.

THere are many things in nature that are both beautiful and dangerous at the same time. PEople learn to appreciate the beauty while avoiding the danger. Many might walk up to teh edge of a cliff for the scenic overview, but they also know not to jump off. Its part of survival of the fittest, natural selection, etc. Homo Sapiens have gotten to where they are today mainly by using their brains. If that cahnges, I have a gut feeling that rock music will have little to do with it.

Harry Partch, who not only was a prolific composer but also developed his own instruments and microtonal scales should also be included in any list of the "underappreciateds".

More than one here, so can't be "most" but perhaps, "very"?...
Edgar Varese
George Crumb

While I do not have first hand experience of their work, from doing a little reading on "minimalism" as it pertains to music, these two names deserve consideration:
La Monte Young
Henning Christiansen