The best thing a mentor can do is challenge you to aim higher and improve yourself.
My mentors were OK with giving me positive feedback, but I wish they had given me more negative feedback. What can I improve? What are my blind spots?
In practice, though, if the people you're mentoring are co-workers in the same company, you have to be more careful about negative feedback because maybe it's not your place to be doing something that sounds like a performance review.
For mentoring junior co-workers, I've found that the most valuable type of information is about how the company works, the idiosyncracies and the "this-is-how-we-do-things-here" quirks. When you're new to a company there's a lot to absorb, and it can be overwhelming. As a mentor, even just being available for questions can be a huge help.
thanks for your input. I find it matches with what I had in mind. So I guess I'm not on a completely wrong track. :)
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