When you give negative feedback, lead w/the opportunity and close w/the benefit.  

You'll accomplish 4 things - 

1. You'll grab their attention,
2. Create a positive tone,
3. Demonstrate your good will, 
4. And motivate 

Example: 

NEGATIVE FEEDBACK TO GIVE - employee repeatedly says "kinda" before making points. 

"I think you can make your points more effectively (opportunity). I've noticed you preface many of your strongest points with the word "kinda" (negative feedback). I fear that waters down the point you're making (explanation). If you eliminate "kinda" from your vocabulary, people are going to be much more confident in what you're saying (benefit)."

By leading with the benefit, you express the "why" up front. The reason behind the feedback is the point, not the feedback itself.