Explanations

Death of Shiro:
From the very begining of GNG a scene was cut where Gin's grandfather (and Riki's father) Shiro is introduced, and it shows how Akakabuto lost his right eye, Kohei his left ear, and Shiro his life.

Ben & Moss?
The reference to Ben and Moss knowing each other already makes sense, because they are each other's stepbrothers. Moss is a pup of two mastiffs and Ben is a pup of the other of these mastiffs and a great dane. In the manga Moss did not have blogs around his eyes, they were just added as a hint in the anime (Info from a reliable source in Japan.)

Wilson attempting to kill the Koga-pup:
The reason for Wilson to revenge the Kogas, has its origins in the past:
The Kogas killed Wilson's family. Londo, Wilson's pup, died instantly, but Lee (his partner) was kidnapped. Later Wilson finds Lee's bones and coat.

Kurojaki wanting to revenge Gin:
Kurojaki, the leader of the Koga dogs, has still got his both eyes but when Gin saves Akame from the Kogas, he strikes Kurojaki's right eye with the sickle, and the dog loses sight from that eye. Because of this Kurojaki wants to kill Gin by himself.

Death of Jinnai, Kirikaze and Madara:
When Gin and Akame are in the forest with Jinnai (Son of Akame) and Kirikaze (Jinnai's bodyguard,) Madara attacks them.
Jinnai strikes from a tree above and happens to fall directly into the bear's mouth and as a result of this he dies. Kirikaze attacks Madara but the bear strikes him deadly in the back. The bear gets killed by cooperation of Gin and Akame, when they detach a large branch from a tree, and Gin thrusts the bear's muzzle with it which kills him.

Death of Terry:
Terry is the same dog which is introduced earlier as Arpe (applause for the translators,) who is the leader of the fifth team. Kisaragi's pack attacked Terry's, and the only way to survive was to join the pack. Moss knows Terry because he was told the names of the pack leaders when they were off to defend the northern territories. Before Gin and the others reach to crater to help them, Terry challenges Kisaragi in a duel. Kisaragi gets Terry dazzled and the dog runs blind into a bush where Mosa kills him.
Before his death Terry said to Kisaragi that compared to those who risk their lives to fight Akakabuto he was nothing. Later Kisaragi remembers this and decides to join Gin and the others.

Great & Vem-scene:
Great gets apart from Ben and the other dogs and meets Vem, a boxer who had got some adic spilt on his head once.
Vem tests Great's loyalty towards the Leader and puts the dog to lie on the railroad track when a train is coming.
Vem with his pack are observing the situation as the train approaches... Then Great's eyes start to bleed, knowing that he won't be participating in the Great Battle against Akakabuto, and this impresses Vem who leaps on the track and saves Great. After this Vem joins Great.

Meeting Hakuro:
Meeting the dog Hakuro has also been cut off. In the real version Ben's pack smells something in the air and Gin leaps to a branch to get a better view, seeing a large pack of dogs approaching. Hakuro is in the lead of the pack and he's laughing.
Nevertheless they stop in front of Ben and the pack and the dogs talk about something. Then Hakuro suddenly attacks Gin but he avoids it and throws Hakuro aside. For some time the dogs talk and then seemingly reach an understanding.

Gathering back to the Leader:
Many people have wondered that "shouldn't they have had to gather at the Leader's cliff after 3 months, there where they had started their journey from. Well, so they did... They waited for the Leader to arrive and when he finally did, the dogs burst in tears and even Benitsakura's legs started to shake and tears fall.

Disappearance of the Leader:
After the above Riki disappears after a fight against an one-eyed bear. Riki attacks the bear with a great "light attack" and cuts the bear's left paw apart, (blood spills.) The pack comes to look for Riki but then a bear attacks them too from a bush.

Sniper & Ben scene:
During the Great Battle Sniper tries to kill Ben by drowning him in a river. Hyena comes to help and gets killed by Sniper. Now Ben gets his chance and throws him into the river which carries him away.

Death of Benizakura:
The sudden death of Benizakura has amazed.
You could say the whole thing started when Mosa attacks Gin's pack while they are looking for the Leader who's gone somewhere and Gin runs into a derelict cottage and finds a piece of rope there. Then they tie Mosa together with the rope they found. Mosa however breaks loose and then Benizakura appears, takes the other end of the rope and pulls the bear in water. At the bottom of the pond Benizakura ties the rope on a tree trunk but as the bear keeps pulling the rope the dogs leg gets stuck between the trunk and the rope. Gin attemps to save Benizakura but he knows that there isn't enough time because he is running out of air, and so Benizakura kicks Gin back to the surface.
The whole pack stares terrified at the point where Benizakura dove, and he might have seen Ben's, Gin's and the others shocked expressions through the water as he finally suffocated.

Death of Akatora:
Akatora gets killed in the Great Battle. One may notice it as only Kurotora and Cyuutora are shown alive.
Akakabuto damages Ben and Akatora comes to help. He attacks the bear but Akakabuto thrusts his neck with his claw.
Using the last strength he has Akatora releases himself from the claw and gets the bear's only eye blinded. Akatora then falls on the ground and dies, and then the dogs attack Akakabuto even more furiously.

Death of Riki:
After Kohei shot Akakabuto after the Great Battle he hugs Gin and Riki but then Akakabuto rises again and strikes Kohei on the head. Riki attacks Akakabuto and Akakabuto strikes Riki also with great power, which makes him slide away on the snow. (Gin is running towards Riki) In a blind fury Riki attacks again but it was fatal, as Akakabuto thrusts his claws in Riki and squeezes him dead.
At the same time Gin leaps in the air, doing the Zetsu-Tenrou-Battoga, the deadly strike, tearing Akakabuto's head loose. The bloody corpse of Akakabuto falls down next to his head.