Colonialism strikes me as a nasty business.  Trade and colonization . . . the Brits forced an opium trade on China, for example; but maybe never colonized China . . . I need to study. 

One thing I am sure of, Colonial Powers tended to disrespect the native, indigenous people, even abuse them.  That is what most white people do to people of color, which is the dominate theme of colonialism, with few exceptions.

I am certain all the colonized were darker skinned and all the colonizers were whte who thought the colony culture need to be "fixed." 

"Map: European colonialism conquered every country in the world but these five"
By Max Fisher              max@vox.com                    Updated Feb 24, 2015

https://www.vox.com/2014/6/24/5835320/map-in-the-whole-world-only-these-five-countries-escaped-european

"It's no secret that European colonialism was a vast, and often devastating, project that over several centuries put nearly the entire world under control of one European power or another. But just how vast can be difficult to fully appreciate.

Here, to give you a small sense of European colonialism's massive scale, is a map showing every country put under partial or total European control during the colonial era, which ran roughly from the 1500s to the 1960s. Only five countries, in orange, were spared:"

Some countries instead fell under "spheres of influence," marked in yellow, in which a European power would declare that country or some part of it subject to their influence, which was a step removed from but in practice not all that distinct from conquering it outright. Iran, for example, was divided between British and Russian sphere of influence, which meant that the European powers owned exclusive rights to Iranian oil and gas in their areas, among other things.

Most of the areas under spheres of influence on this map were politically dominated by the British, who ruled through proxies: Afghanistan (which also endured Russian influence), Bhutan, and Nepal. Mongolia was effectively a proxy state of the Soviet Union for much of the Cold War.

Something similar happened in China, where European powers established parts of coastal cities or trade ports as "concessions," which they occupied and controlled. Some, such as Shanghai, were divided into multiple European concessions. Others, like British-controlled Hong Kong, were fully absorbed into the European empires. This is why China is labelled as partially dominated by Europe."

Power seems to come from domination.  Domination apparently required a military or police aspect, where the colonizers had to "beat" (any form of physical or economic force) the colonies into submission.

"Which colonial power was the worst (most oppressive, provided fewest benefits to colonised, resulted in legacy of discrimination/conflict) and which the best (most humanitarian, provided responsible transition to independence, etc.)?"

https://www.quora.com/Which-colonial-power-was-the-worst-most-oppressive-provided-fewest-benefits-to-colonised-resulted-in-legacy-of-discrimination-conflict-and-which-the-best-most-humanitarian-provided-responsible-transition-to-independence-etc