8 – TRAFALGAR D. WATER LAW vs DONQUIXOTE DOFLAMINGO
Law used to be a subordinate of Doflamingo’s. Law and Doflamingo got along quite well, as Doflamingo viewed him as his little brother.
Law later discovered how little Doflamingo actually cares for him and, after the latter revealed to Corazon that he intends to “educate” Law to die for him via brainwashing through the Ope Ope no Mi’s immortality operation, coupled with Doflamingo murdering Corazon, who saved Law’s life by giving him his Devil Fruit to cure his illness, Law defected from Doflamingo, swearing to avenge Corazon’s death.
After the betrayal, Doflamingo wanted Law to die in a terrible manner that he would regret ever being born. The two would already be eternal enemies towards each other due to Law’s nature as a “D.” and Doflamingo’s status as a former World Noble, something Corazon was already aware of.
7 – MARSHALL D. TEACH “BLACKBEARD” vs SHANKS
Shanks has a watchful eye out for Teach. Although exact events are unknown, Shanks previously admitted to Whitebeard that his facial scar came from a direct attack from Teach. Shanks himself seems to know the potential danger Blackbeard represents is greater than that of anyone else.
Even at Marineford, Shanks addressed Teach in a tense manner, and he only seems to regard Teach as a significant threat compared to the Marines or the Whitebeard Pirates and their New World subordinate crews.
Having already proclaimed “his” era is beginning, unveiling the new members of his crew and demonstrating control over two Devil Fruits, Teach said he had achieved his goal for the time being, while also knowing he was not ready to face the Yonko.
6 – AKAINU vs KUZAN
Kuzan detests Fleet Admiral Sakazuki, because the latter follows a policy of “Absolute Justice”. This disgust dates back many years, as during the time when both were still vice admirals, Sakazuki killed innocent Ohara civilians to ensure that none of the archaeologists escaped the Buster Call, causing Kuzan to call him a fool. After Sengoku resigned, Admiral Aokiji was strongly opposed against Admiral Akainu becoming fleet admiral and fought him for the position, even though Kuzan himself originally had little interest in it. They battled for 10 days, but Kuzan was defeated and he resigned from the Marines rather than serve under Sakazuki.
5 – SHIKI vs GOL D. ROGER
Shiki is one of the many Pirates whose utmost respect had been gained by Roger. In fact, during their youth, the two Pirates flew into several skirmishes against each other due to their separate ideals (Shiki wanted to control it all, while Roger simply wanted to remain free), but in their last battle, Shiki was shown to be willing to treat the past as letting bygones be bygones, if Roger would just agree to form an alliance with him, and was even ready to work together with the Pirate King for his grand dream of conquest, offering to have the known world as spoils.
When Roger was “captured” by Marines, Shiki angrily invaded Marineford, saying that he should have killed him himself, and when in Impel Down, he thought of his old rival, showing sadness because of all the new rookies wanting to invade the Grand Line, and veterans like Roger dying.