Four comments.
First: if you're involved in an online discussion, and your interest is in arriving at a greater truth rather than promoting some previously established premise, you might care to consider the principle of charity, that is: reading your interlocutor's comments in the most charitable way possible. http://philosophy.lander.edu/oriental/charity.html
In part:
The principle of charity is a methodological principle—ideas can be critiqued after an adequate understanding is achieved. The original presumption of setting aside our own beliefs and assuming the new ideas are true is only a provisional presumption.
Secondly, you're committing whataboutism, or more formerly, tu quoque. The behaviour of governments, of themselves, has little bearing on the behaviour of corporations.
More significantly, power and aggression are not limited to any one form, they exist independently, and are innate in any number of institutions (or no institutions at all).
You may be familiar with the concept, and perhaps hold it against governments, that they claim a monopoly on the use of force. If you'll trace the origins of that comment, it comes from Max Weber, who ascribes to government a monopoly on the legitimate use of force. That is: it is only governments who can claim that legitimacy, and the concept doesn't mean an indiscriminate use of force.
If you don't grant the monopoly on legitimacy to governments, then you are allowing legitimacy to other institutions, possibly any institutions. Force and abuse of power are innate. They don't exist only in government, they exist independent of government.
What government is, is a structure, a mechanism, for channelling and controlling political power, and attempting to use it, accountably to some vault of power itself (the people in a democratic or republican government, other sources in others), for the improvement of society as a whole.
As with all machines, they sometimes malfuntion. As with many machines, they have a tendency to not function properly. The incidental failures are not of themselves an indictment of the concept as a whole.
And, if you remove government, or worse, align it, without accountability to the people as a whole, in the interests of business or pecuniary interests alone, you end up with the worst of abuses. You may or may not be familar with some of these:
The settlement of the Americas, through what might be considered a public-private partnership on the part of several nations (Spain, Portugal, England, France, Holland, Russia, largely), resulted in the genocide of a native population once numbering perhaps 40 - 50 millions. What this lacks in the intensity of nuclear annihilation, it greatly exceeds in magnitude.
The public-private partnership of Belgium in the Congo saw untold atrocities, including the unhanding of hundreds of thousands or millions of Congo natives. See Joseph Conrad's The Heart of Darkness.
Or of England, the East India Company, its private government and army within India, and the Opium Wars against China -- chemical, biolical, and conventional war against two entire cultures.
Labour unionisation, a concept and principle defended by Adam Smith, John Stuart Mill, and other classical economists, say violent opposition by factory and mine owners particularly in the UK and United States. U.S. Steel, the West Virginia Mountain Wars, the Wobblies, the Triangle Shirtwaist Factory fire, and more.
Industrial accidents have killed or destroyed many tens or hundreds of thousands: the Halifax, Galveston, Port Chicago, and West, Texas, explosions -- some entirely private, some public-private partnerships. Mining accidents claimed an average of greater than 2,000 lives/year for much of the first half of the 20th century, statistics tabulated by the US Department of Labour, and available online. That's on the order of 100,000 souls over the century, virtually all of their deaths preventable. The Union Carbide Bhopol disaster. Dam failures, including Johnstown, in the United States (this was the instigation of the Red Cross as a disaster releif organisation, and of significant concepts expanding liability law). For public-private parternships, the Vajont dam disaster, claiming 2500 lives. And showing that poor management, planning, engineering, and response aren't solely the remit of nominally capitalist societies, the Banqiao Dam disaster of 1975, in China, in which some 170,000 souls perished, on par with your nuclear bombing example, though it was but 25 thousands who died immediately from drowning, the others were lost due to starvation and disease in the following weeks -- as I said, exceedingly poor planning and response.
For raw corporate aggression, I'd suggest the Johnson County War:
On April 5, 1892, 52 armed men rode a private, secret train north from Cheyenne. Just outside Casper, Wyo., they switched to horseback and continued north toward Buffalo, Wyo., the Johnson County seat. Their mission was to shoot or hang 70 men named on a list carried by Frank Canton, one of the leaders of this invading force.
I've written on this previously: https://ello.co/dredmorbius/post/xwjjk1bh7yki6ja4lrg7ka
There is the insidious poisoning of millions through lead, asbestos, tobacco, mercury, and dioxins, both generally and across specific sites, all whilst paid corporate shills actively and deliberately sowed confusion on the matter, knowing full well that their position was false. Naomi Oreskes and Eric Conway have covered much of this history excellently in Merchants of Doubt.
And there's the little matter of carbon dioxide emissions and their effects on global tempeatures and ocean chemistry, known since the 1880s, and recognised as a major threat since the 1950s, but still actively denied by numerous interests more concerned over their trillions of dollars of accumulated wealth and power than over the fate of the planet they live on and the souls they share it with.
What Rothbard's "non-aggression principle" (a very late add to the Libertarian theology) does is to preemptively disarm those who would seek to employ wealth and power without limitation. It is an exceedingly bad principle for the citizenry.
But as you were saying.