Based on quality:
* Low-quality papers: This simply indicates papers that are poorly written, poorly researched, or lack credibility.
* Substandard papers: Similar to low-quality, but perhaps suggesting a lower level of professionalism or adherence to academic standards.
* Junk papers: This implies papers that are completely lacking in value or credibility, often containing misleading or fabricated information.
Based on format:
* Informal papers: This refers to papers that are not written in a formal academic style. They might be more casual or written for a specific audience.
* Non-academic papers: This refers to papers that are not written for academic purposes, such as news articles, blog posts, or personal essays.
Based on purpose:
* Non-research papers: This refers to papers that are not intended to present original research findings. Examples include opinion pieces, reviews, or summaries of existing research.
Other options:
* Mediocre papers: Papers that are neither particularly good nor bad.
* Unreliable papers: Papers that cannot be trusted because of questionable sources, biases, or lack of evidence.
To give you a more precise opposite, please provide more context. What kind of papers are you thinking of? What are you trying to contrast them with?