Objectively, we can say Bandana's leadership has not been good because it led to her getting hit in the head with a wrench.
I mean, I don't know if she could've done it any better or if any changes would've improved the situation. But the ideal outcome of her leadership would probably include not getting wrenched in the head.
Maybe she could've been less insulting at that last point - try to keep her cool and her tongue when dealing with an annoying subordinate. Long-term, she could've tried to address Andi's obvious bitterness - ignoring a person's resentment towards you is a good idea in most relationships, but not when dealing with an employee. "Brushing off haters" is tough when said haters work for you and their performance is vital to your efforts. That's an important management lesson for us all - never ignore an employee's grievances. You don't have to give in to those grievances, but you do need to address them, because otherwise you're just ignoring a problem that will only grow bigger and bring down the whole team.
But c'mon - it's Bandana's first management position. She'll learn ... unless there's permanent brain damage from the aforementioned head-wrenching. But now we learn the important function that Human Resources provide. This could have all been potentially avoided with a proper HR department on-board the Mechane to hear out Andi's grievances, to mediate a discussion with Bandana, and to provide Andi with workshops on Anger Management and Constructive Criticism.
So really, this is ultimately Julio Scoundrel's fault for putting together a faulty corporate structure and a management system based primarily on Charisma checks.