The fight was a vision that Alice showed Aro. Aro sees himself dying and leaves peacefully. Bella, Edward, Renesmee, Jacob and the rest of the Cullens live happily together forever.
Bella (Kristen Steward) awakens from her transformation into a vampire (from BD Part 1) and reunites with Edward (Robert Pattinson) and their child Renesmee. Renesmee, being a human/vampire hybrid, grows very quickly which concerns the Cullen clan as no other child like her is known to exist. While Bella, Renesmee and Jacob (Taylor Lautner), who imprrinted on Renesme in BD Part 2, are walking one day, Irina, a vampire who loved Edward and is jealous of Bella, sees the three and assumes that Renesmee is an immortal child a child who is turned into a vampire during its formative years. The Volturri stricts forbids the production of immortal children and the punishment is death to the child and its creators. The Volturri decide to attack the Cullens but Alice sees them coming and in order to defend themselves, they attempt to gather as many witnesses among their friends to prove that Renesmee isn’t an immortal child.
The day of the battle arrives. The Cullens, the wolves and about a dozen of the vampire witnesses stand against Aro (Michael Sheen) and the Volturri soldiers. Renesmee “shows” Aro that she is not an immortal child through her special power of communication and Aro concedes. He has Irina killed for bearing false witness. Alice and Jasper reappear after having fled weeks earlier in order to avoid capture from the Volturri and she shows Aro a glimpse of the future if the Volturri decide to attack anyway it would lead to the total destruction of Aro and all of his men. Alice also presents them with another haf human/half vampire named Nahuel whom she found in Brazil a man who bears no threat to mankind for his unique “halfness”. The Volturri decide to leave in peace and the Cullens bid farewell to their vampire friends.
Weeks later, Bella and Edward have settled into their peaceful life. Renesmee continues to grow and we learned that Nahuel was about 150 years old but had reached full maturity seven years after his birth. So Renesmee can expect to have a long life with Jacob at her side.
In the end, Bella taps into her power as a “shield” to show Edward her thoughts, a montage of their first meeting up to their marriage. Bella says no one has have loved someone more that she loves Edward and Edwards asks to read her thoughts again.
Thanks Sarriesleepers (Long) and Nicole (Pooper)!