How do you differentiate between a good leader and a bad leader?

Simple actually. Good leaders have leaders who independently run their responsibility.

Poor leaders are involved in everything.

Now, there can be many reasons various leaders are or are not involved in things but the question asks for the stark distinction that a VC can draw: A founder who needs to be involved in everything is a poor leader.

A good leader will attract other leaders. A good leader will inspire, lead, and delegate to others more capable. A good leader doesn’t manage, they lead.