Often a question is asked as to why Rama killed Vali in hiding? If Rama was powerful he should have openly challenged Vali .
People also interpret that maybe Vali was more powerful since Vali also had the benediction of getting half the strength of the opponent.
The experts of Ramayana give us a very practical and profound answer in regards to Sri Rama’s strategy, here it goes:Vali was arrogant, insensitive and punished his opponent and subjects more than required.
For him no opinion was valuable unless it came from himself. He was powerful, but this did not matter to the people of Kiskinda .
They preferred a change of King, in the form of Sugriva. Attacking the entire country for bringing about this change would cause massive blood-shed . Hence Rama thought it would be better to kill him alone, without giving much information and scope for speculation of Lord Rama’s attack on Kishikinda.But why hide?Rama knew very well that, Vali was bad, but he was not a demon like Ravana.
Vali had some religious sentiments. If Rama would declare his identity openly, Vali would politically surrender but not from his heart, and would say, ‘I can easily bring Sita back from Ravana.” In fact this is what he said, as he lay down hit by the powerful arrow of Lord Rama. He said “ why did you not ask me about your Sita, I could have easily done this task.” Lord Rama did not want to take help from a person who had committed similar crimes as Ravana. Vali had abducted the wife of Sugriva, by force. So taking help form him would mean supporting one person for the very crime for which he wanted to punish another.
So Vali needed to be punished, and that had to be done in a way where Vali had no chance of using any strategy. Lord Rama had to checkmate.Thirdly, Rama did not want to enter Vali’s kindom, thereby giving no iota of speculation to the people of Kishkinda about Rama trying to remote control the kingdom. He allowed Sugriva to take compete control over the kingdom, and Sugriva asserted his authority over Kishikinda not as a representative of Rama, rather as the king chosen from amongst their own people. Although personally Rama had became Sugriva s worship able deity.Rama as a last stroke of strategy, assured the protection of Tara, Vali’s wife, by by asking her to marry Sugriva as per the custom of Kishikinda.
The custom was different from Ayodhya but Rama did not superimpose his rules in another kingdom, and at the same time Vali’s son was made into prince .Even if we consider that it was injustice to Vali, but collectively if we see it was everybody’s gain.
Most importantly a good and sensitive leader would lead Kishikinda who was guided by a selfless intelligent, powerful innocent, heroic and devotional, adviser, like Hanumana.