I tend to disagree slightly, though I don't see why you're downvoted (I don't think you should downvote a civilly written comment just because you disagree).

China was subject to colonialism, but not in the same way as India; it was never fully controlled by colonial masters like the British controlled India. There were colonial enclaves and much of humiliation with being forced to hand over areas for trade posts; there were the opium wars and later there was the Japanese expansion and imperialism, but the deep Chinese countryside was always managed by the Chinese for the Chinese.

And there were decades of unrest and civil war. But still, I don't see how China was suffering from colonialism more than India.

They both had their hardest times in their early independence after colonial times. China with civil war, Great Leap Forward, Cultural revolution; India with jumping to the Soviet boat, socialism, planned economy and protectionism.

Korea, on the other hand, has throughout its history been a smaller nation which bigger neighbours try to run over. Sometimes - like in the case of Japan in earlier half of 20th century - it has indeed been completely overrun for decades. So, to survive, it has become fiercely nationalistic. But Korea also definitely faced absolute full scale colonialism, in my opinion in much more depth than India.

But China suffered from warlords and persistent low level violence for the first half of the 20th century

Definitely, but that was not colonialism. The warlords were Chinese; the power bases for these warlords were built during the late Qing dynasty. They of course had some Western influences (one even proclaimed himself Christian, another announced he was admirer of George Washington) but primarily they were just Chinese men of power, with short-term visions that were ultimately defeated by determined nationalists.