Sir John Hawkins started the Brits into the slave trade, which ended up a monopoly venture, supplying all the other european empire colonies in the New World.
The British started the protest against slavery in the 1770's, which obviously caused the American Colonists to have conniptions. The South Carolina rice plantation owners went into overdrive and enlisted the Royal Courts of Russia and France to give impetus to a quick secession, things like the Boston Tea party were symptoms of mass hysteria whipped up by the wealthy slavers. The British Empire made laws forbidding Britons to participate in slave trading in 1807 and outlawed it in the Emancipation Act of 1833.
I don't know of many Empires that would equal the British one and I'm not too sure any of the others had the social conscience to invent an unstoppable industrial revolution, encourage science and innovation without religious interference, emancipate slaves, empower and universally educate the working class, give rule of law and parliament to the world.
You seem to fixate on a 400 year seemingly brutality that by comparison to their contemporary European counterparts was sublime and by any measure was far less barbarian than the cultures they subdued. You only have to look at how the Islamic thugs behave to get a glimpse of primitives who need civilising. Romanticising of cultures only a few generations back as somehow benign and benevolent being victimised by whitey are fanciful by any measure.... it wasn't that long ago that our Christian educated Australians freed the sub continent from Japanese warlords who enjoyed the genocide of Chinese cities and the brutal enslavement and indiscriminate mass killing and torture of SE Asian peasants, far worse than the dick4ea9 French.
A bit too early in the year for this kind of rationalisation isn't it Captain Arthur McGee? Shouldn't we save these for Australia Day, or the Queen's Birthday perhaps?
The problems with Empires are not so much its "peace" years, it's the years of slaughter preceding those years of peace and harvesting.
So take what you said above... Hawkins started the British slave trade, monopolises it and a few years later British imperial civility banned its trade in 1807 then outlawed it in 1833.
Oh look, the American Revolution kicked the Brits out by 1783, Napoleon and his French Empire was mucking around ruining British interests; and look, the Industrial Revolution kinda pick up around the early 1800s too.
A few happy coincidences of kindness and humanity that also serve Britain's own industries while weakening those of their former colonies and peer rival.
I thought genocide is genocide. How does one do it more nicely? Less barbaric-ly?
Does driving them into the desert and let nature deal with them more civilised than, say, gas them or bury them alive in mass graves? Does killing the buffaloes that is their main source of food, shelter and industry more enlightened than having to send out the cavalry to take them on?
So the Nazi didn't see their warmongering as peace-keeping? Imperial Japan didn't see them butchering cities and starving the colonies as sacrifices to be made so that all of Asia can rise to more enlightened position within a unified empire?
As to the British empire... Alexander's was quite nice to his conquered territories. All he did was renamed their cities, give a standard rule of law and set up a few governors. Other than that, the country can just bury its dead and carry on as normal.
Same with Genghis Khan and its various Khannates all over the place. Same with Napoleon and his Civil Code... did you know his need for a secured source of supplies led to canned food we all enjoy today?
Or take Chin'a first emperor. All he did was slaughter a about 7 other states nearby; standardise the legal code, dress code, language, money and systems of trades and administration... then they all became one big happy family of Chin when the Han took over and further pacify the nearby barbarians.