I've had two piano teachers.
The first one was fun, vibrant, lively and encouraging, though she still made constructive criticism. She made me try out all different genres of music, and she was always willing to let me try something new. I suppose she was a bit unconventional at places, but I think her personality was the reason why I never had those "OH I want to quit right now" phases at all.
My second piano teacher is much older (nearing her 80s), and perhaps more focused on the technical side than my previous teacher. But I think this was an improvement; now I know my scales inside out. She also likes to go into great depth into something completely off-topic which is always fun

She is a good pianist and a lovely 'granny' type lady. I get on very well with her.
My clarinet teacher... I've had two for this too:
The first one was really, really, really nice. She never made me feel small, or ashamed, or bad on the clarinet. I suppose she didn't make as much criticism, but it was fun going to her lessons.
My second one... uh.... she's OK, is all I can say. She has a tendency to play along with me, which REALLY puts me off. I get on with her well enough.