One major Reason Rama killed Vali is because Sugriva’s wife was taken over by Vali. Ram also had similar problem as his wife was kidnapped by Ravana and he needed the help of Sugriva to find her. Kabandha says it in few words. 3-72-7b&8– When kings are in trouble they employ one of the 6 tactical moves (The six ideations employed by kings in kingship are 1] sandhi (सन्धि)a covenant with adverse kings; 2] vigraha (विग्रह)continuing hostilities; 3] yaana(यान)waging war; 4] aasana (आसन )sit out for proper time; 5] dvaidhii bhaava(द्वैध भाव) creating factions and vicissitudes in enemy groups; 6] samaashraya (समाश्रय)taking shelter under a coequal.) The one suggested by Kabandha is the 6th one, joining force with a person of equally vulnerable position. Both Rama and Sugriva have lost their kingdom and their wives.
But there is difference. Whenever Sugriva identifies his problem he says regaining my wife and Kingdom. Kingdom was never his but at least he loves his wife and is bereaving for her,may not be to the same extend as Rama. Sugriva himself says I did not despair like this for my wife 4-7-6. So when Vali gets killed what would you expect. Sugriva is having nice time with her. No. When angry Lakshmana goes to Kishkinda to express his anger 4-31-22 the lustful Sugriva is with whom? Tara (Vali’s wife). So what exactly is Valmiki telling us. In fact the whole of Kishkinda kanda is a Jigsaw puzzle of Justice in quandary (Dharma sankat). Now the explanation of Killing Vali is going to be more difficult!
List of Slokas
शृणु राघव तत्त्वेन यथा सीमाम् अवाप्स्यसि || ३-७२-७
राम षड् युक्तयो लोके याभिः सर्वम् विमृश्यते |
परिमृष्टो दश अन्तेन दश आभागेन सेव्यते || ३-७२-८
|Oh, Raghava, how you will regain Seetha, that you listen from me in its essence… oh, Rama, by which and which analyses everything will be analysed, six of such ideations are available in this world… and when a person is touched down by a spell of nemeses, he shall adore one who is equally in such spell of nemesis… Back|
मया अपि व्यसनम् प्राप्तम् भार्या विरहजम् महत् |
न अहम् एवम् हि शोचामि धैर्यम् न च परित्यजे ||
|Upon me too this yearning caused by the separation of wife has chanced, but I did not despair this way, nor I have forsaken my courage… Back|
तारया सहितः कामी सक्तः कपिवृषः तदा |
न तेषाम् कपि वीराणाम् शुश्राव वचनम् तदा ||
|At that time, he who is in a lustful mood, who is in the company of Lady Tara and who is enmired in privacy, that foremost monkey Sugreeva is unheedful of the words of those bold monkeys who brought the message. Back|
All Sloka Translations are from the site Valmiki Ramayana