It is a good leadership practice to give constructive feedback. What are we typically trying to achieve? We want others to do something different in the future, something that will improve their performance. The expected change will benefit the other person or you or most likely both of you. Think about this: How likely will this happen when this individual leaves your dialog feeling frustrated or even humiliated? Great leaders inspire with feedback even if the circumstances are difficult.
You’re under pressure because you definitely started this important project too late. How