Way 1 · best default
That's really impressive
Clear and sincere. Works for skills, results and achievements, with anyone.
Examples
You learned all that in six months? That's really impressive.
That's really impressive, I could never speak three languages.
In a conversation
A: I built the whole website myself over the weekend.
B: That's really impressive. It looks professional.
Common mistake
Not: You make me impressive.
Say: That's really impressive.
The thing is "impressive". The person who feels it is "impressed": I'm impressed, that's impressive.