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?
Your title asks a different question than your post: "useful" vs. being a "social virtue."
Consider two companies: A and B. Each has the option to pursue some plan X, or its alternative Y. X is more ruthless than Y (X may involve laying off a large portion of their workforce, a misinformation campaign, or using aggressive and unethical sales tactics) but X also stands to be more profitable than Y.
If the decision of which plan to pursue falls to a ruthless individual in company A, company A will likely pursue X. If the decision falls to a "highly competitive, compassionate, with restrictive sense of fair play" individual in company B, B may perform Y instead. If B does not perform Y, it is likely because they noted the comparative advantage A would have, being likely to pursue X. In this case, it is still in B's interest to act ruthlessly, making ruthlessness useful.
Now, is it a virtue? Well, for a particular company it is useful: it allows the pursuit of plans that would otherwise not be followed. Does the greater society benefit from it? Well, society gains whatever benefit is gained from business pursuing such plans, at the cost of whatever the costs of such plans are. But it is a useful enough character trait for one company's executives that it grants a competitive advantage over other companies where that trait is absent. Thus, it is an advantage- and perhaps a virtue, I am not sure how that word cashes out here- for each company. Companies without ruthless executives may fail to act or fail to act quickly where a ruthless executive wouldn't hesitate. So in situations where ruthless tactics allow one to win, ruthless individuals are an asset.
I'm not sure what more can be said on this, as I don't have a good way of cashing out the word 'social virtue' here or what practical question you are asking.
I chose a somewhat misleading title deliberately, although I can understand if people take issue with that. As I acknowledged in the post itself, it's clear that ruthlessness can be useful from the perspective of individual companies. From the perspective of a person judging their value to society, it's not so clear that ruthless business executives are useful. Their competitive advantage may lie purely in allowing them to make decisions that are in the company's interest, but not the public interest.