(Life's too short to reference all this stuff! And I'm sure it's not original...)
According to some accounts, Hegel's last words, to a student, were "you were the only one who understood me ... and you got it wrong." My favourite variant is, "No-one ever understood me. Even I don't understand me." Which doesn't surprise me. I have actually tried to read him (in translation, I confess); I've just picked Reason in History (1837, tr. Hartman; New York, Bobbs-Merrill, 1953) off my shelf. [Next, I confess, to Spencer L and Krauze A (1996) Hegel for Beginners Cambridge; Icon--the spine of which appears never to have been creased...] But the guy blathered so much, it's almost impossible to make any judgement of his value. Although of course Kierkegaard had a good go. And so did Marx, from a different angle...
So--having established my lack of credentials for expressing any opinion whatever; his Big Idea was the Dialectic (even if Socrates got there first). It's the fundamental principle accounting for History (leaving aside all the metaphysical accretions).
Actually, it's simples; it's even common sense. Thesis: an idea (principle, value, etc.) meets Antithesis (conflicting idea, etc.) and the outcome of the encounter is Synthesis; compromise, etc. but sometimes a new Idea which can embrace and subsume its progenitors.
Except that it doesn't work. Hegel was an Idealist, in philosophical terms. In the Real world, however, there is always detritus. In history and politics and culture, two opposing positions rarely resolve into one, but into three; residual hard-line "no surrender" thesis--fragile synthesis--residual hard-line "no surrender" antithesis.
Two begets three... Think Northern Ireland even now; think Anglicans on women priests/bishops; ... and currently think the US government.