The interviewer wants to hear that you only speak positively about your past manager. Think about the things that you enjoyed about this person and their leadership style. Start off by telling the interviewer some things that you liked about their style. You might talk about how they had regular team huddles to provide ongoing communication about process changes or upcoming events. You might share how they regularly had fun activities going on to keep the team engaged. Keep the focus on the positive things.
"My most recent manager cared a lot about the success of the company. For that reason, she always ensured that we were properly trained and up to date on new happenings within the company. She was sometimes late for work which was a bit frustrating but that aside, she was a great manager."