I'm not sure there's a definitive list; there are many kinds and styles of mentors. Some are tough and hard to get along with (even if they might be generous or have great insight). Some mentors are gentle. Sometimes you have a great mentor but no personal connection.
I think there are some preferred qualities: listening; open mindedness; vulnerability; inclusiveness.... but I've been mentored by someone who had no time for my stories, felt they had all the answers and never showed a weakness. At the time, I wasn't sure the relationship was taking my thinking in any new direction; turns our it was and for the better.
I think if you know why you are approaching a particular individual for mentoring (with a goal in mind that only they can help you examine), then that's the place to start. You might have an ideal style in mind - as a mentor you might aspire to a certain style. But I believe it takes all kinds of folks to walk us through all kinds of approaches and thinking. I'd like to hope that those who mentor offer a kinder/gentler space but part of success is learning to form relationships with all kinds of folks. So have all kinds of folks as mentors then makes sense?