Focusing on the negative effect:
* While the new policy aimed to improve efficiency, its unforeseen consequences proved deleterious to the company's morale, leading to increased staff turnover.
* The excessive use of antibiotics, though initially helpful, can have a deleterious impact on the gut microbiome, potentially leading to health complications.
* The constant exposure to air pollution, although often overlooked, is known to have a deleterious effect on lung health, especially in children.
Highlighting the contrast:
* Despite the initial excitement about the new technology, its long-term effects, unfortunately, proved to be deleterious, hindering innovation instead of promoting it.
* The economic downturn, though initially seen as a temporary setback, ultimately had a deleterious effect on the nation's infrastructure, leading to widespread neglect.
* Although the research initially showed promising results, further studies revealed a deleterious side effect, prompting scientists to reconsider the application.
Using a relative clause:
* The widespread use of pesticides, which are known to have deleterious effects on the environment, has been a subject of intense debate.
* The company's decision to relocate its operations, a move that proved deleterious to the local economy, was met with widespread criticism.
Adding a dependent clause:
* The government's decision to cut funding for public education, which could have a deleterious impact on the future of our society, has been met with widespread disapproval.
* The athlete's constant use of performance-enhancing drugs, though initially boosting his performance, ultimately had a deleterious effect on his health, leading to a premature end to his career.
Remember to tailor the sentence to your specific context and purpose. The key is to clearly express the negative impact of something and to make the sentence grammatically correct.