With critical feedback, ask if it resonates with the listener and have a discussion. This can help them fully process and understand what you’re talking about. “What are your takeaways and next steps?”
Summarizing in writing can also help consolidate the conversation and highlight miscommunications.
You can also try to bring the feedback from many different angles (see 360-degree feedback adds objectivity by adding perspectives (Zhou)). You can also ask peers to provide feedback directly to each other rather than being a middle man.
Reference particular anecdotes to make your feedback concrete.
Paint the brightest goal post you can. Sometimes this is practical, sometimes it describes the feeling instead.
Sometimes you want to let the person figure it out themselves to help them grow, but you can also suggest specific possible next steps to help guide them to success.
Julie Zhou, The Making of a Manager