Weapons merchants. Privately owned prisons. Beneficial to the society they operate in, as you specify. I would not call them brimming with ruth. The Zeta Cartel is beneficial to some of the society it is in at least, but is outside the law and exceptionally ruthless.
Yvain covers the issues with privately owned prisons in his non-libertarian FAQ. In what respect do you think ruthlessly run private prisons are beneficial?
When it comes to weapons dealers, I concede that if you consider the country in which they are based, and not the countries to which they make their sales, to be "the society in which they operate," then increased ruthlessness is likely to result in increased enrichment of their society. If you count net gains by ignoring associated costs incurred elsewhere, then there are certainly "ruth...
We have a tradition of treating ruthlessness in businesspeople as something of a virtue. Certainly, ruthlessness can help one get ahead in the business world, and companies often benefit from executives who're willing to put aside scruples while devising means of turning a profit. So ruthlessness in business executives can certainly be useful for businesses.
From a societal perspective though, businesses are only valuable to the extent that they increase the wealth and quality of life of society as a whole. Businesses are allowed (indeed, required, in the case of publicly traded companies) to attempt to maximize profits, on the presumption that in doing so, they'll enrich the broader society in which they operate. But there are plenty of ways in which businesses can increase their own profits without becoming more wealth productive, such as cooperating with competitors or establishing monopolies in order to keep prices artificially elevated, use of advertising to promote a product or service relative to equal or superior competitors, lobbying with politicians to slant the legal playing field in their own favor, and so forth.
I have reasons to expect myself to be somewhat biased on this issue, so I'm not sure how telling it is that I personally come up short of any examples of ruthlessness in business executives being useful from a societal perspective, when compared to business executives who're highly competitive, but compassionate, with restrictive senses of fair play. So does anyone else have examples of ruthlessness in businesspeople as a social virtue?