3-Gol D. Roger vs Monkey D. Garp
As a Marine, Garp attempted to kill Roger several times. Gol D. Roger stated that he and Garp had almost killed each other on numerous occasions.
2-Mihawk vs Shanks
In the past, Shanks and Mihawk sought out each other on many occasions to duel. Their battles were said to echo through the whole Grand Line. I hope Oda will show a flashback of these fights in future.
1-Monkey D. Garp & Gol D. Roger vs Rocks Pirates
38 years before present time, a battle between the Rocks Pirates and a joint effort of the Roger Pirates and the Marines took place on the island God Valley.
For unknown reasons, the world nobles and some of their slaves were present at God Valley during this incident. In order to protect them from Rocks D. Xebec and his crew , current Marine vice-admiral Monkey D. Garp had to form a temporary alliance with Gol D. Roger, captain of the Roger Pirates.
The Rocks Pirates were considered to be the most dangerous and strongest pirate crew of their time; they had at least three of the four future Yonko (Whitebeard, Big Mom and Kaido)
Eventually, it took the combined strength of Gol D. Roger and Monkey D. Garp to defeat them, leading to Rocks D. Xebec’s death and the crew’s disbandment.