A recent study from Harvard Business School found that even if a worker is a star performer in terms of productivity, if they're toxic it's still better for net profitability to avoiding hiring them. 

The study defined a toxic worker as someone whose behavior is harmful to the organization, either its property or its people. This can range from, at its most harmless, to someone who just doesn't fit into the company and, at the other end, people whose actions can, if discovered, prompt intervention from regulatory or law enforcement agencies. In general, though, these types of workers can have harmful effects such as customer loss, lowered employee morale, higher turnover or loss of legitimacy among important external stakeholders.

Another curious feature of toxic workers, according to the study, is that they are"much more productive than the average worker" meaning that "there is a potential trade-off when employing an unethical person: they are corrupt but they excel in work performance. This might explain how a toxic worker can persist in an organization." 

After looking at a dataset of over 50,000 workers across 11 firms, however, the researchers concluded that this still doesn't make up for the damage they do to the company. Turnover costs alone generated from their actions cost the company $12,489 each, and this isn't including effects like lost morale or regulatory actions. By contrast, according to the report, hiring a superstar worker (the opposite of a toxic worker) generates savings of about $1,900 to $5,300 each.