The opposite of "no slack" is "some slack," which means to ease up or provide leeway or flexibility. Other antonyms for this phrase include lenient, relaxed, permissive, and indulgent, which all suggest a more tolerant or forgiving approach. In contrast, antonyms that convey a strict or demanding attitude include rigid, uncompromising, harsh, and unyielding. When it comes to work or performance standards, "high standards" may be an appropriate antonym for "no slack," indicating an expectation for excellence and precision. However, in personal relationships or communication, being too strict or inflexible can create tension or conflict, so "some slack" is often preferable.