* Lenient: This is a good general antonym, meaning merciful or tolerant.
* Lax: This implies a lack of strictness or rigor.
* Flexible: This suggests a willingness to adapt or change rules.
* Permissive: This means allowing or permitting something.
* Easygoing: This describes someone who is relaxed and not easily upset.
* Loose: This can describe rules or standards that are not strict.
The best antonym will depend on the specific situation and the meaning of "stringent" in that context.