Under Bagheera training, Mowgli is failing in matching the skills of foxes in the pack.
Bagheera is forcing him to fight like a fox which will help him to fight against Sher Khan.
Mowgli survived once from Sher Khan, But he is not ready to face Sher Khan.
Baloo identified What Mowgli is capable of? He let Mowgli himself.
Bagheera is not happy about it.
In the end, Bagheera asked Mowgli to fight as yourself.
Mowgli killed Sher Khan.