Antonyms for the phrase "giving a leg up" could include hindering, obstructing, impeding, thwarting, and stalling. These words all imply actions that prevent progress or advancement, rather than assisting it. Providing obstacles or actively working against someone's success can be detrimental to their growth and can build animosity within relationships. Instead, we should strive to uplift and support one another, encouraging their talents and providing opportunities for growth. Let us use positive words and actions to promote success and push each other towards greatness.