In the "Wano" arc of One Piece, the tragic death of Kozuki Oden was revealed, leaving fans wondering why Whitebeard, who so deeply valued his crewmates, did not avenge him. Despite the fact that Oden had joined Roger's crew despite being the Whitebeard Pirates' Second Division Commander, Whitebeard and Oden's bond had not been broken. Because they were both sworn brothers, one can only imagine how upsetting Oden's death was for Whitebeard and his crew.
Given his massive crew, treasures, and extremely talented fighters on his side, Whitebeard could have gone up against Kaido, but he didn't. Even more perplexing is how he waged a full-fledged war against the Marines to save Ace while passively accepting Oden's death. However, just because he did not act does not mean that Whitebeard was not crushed by the loss. Here's why Whitebeard didn't avenge Oden's death.
Oden and Whitebeard's Relationship in Complete Form
Oden chased him relentlessly, and Whitebeard finally gave in and let him join his crew. Oden quickly rose through the ranks and attained the position of commander after joining the family of the Whitebeard Pirates and even being regarded as Whitebeard's younger brother. He eventually left with Roger, but he did so amicably with Oden.
Oden never went back to the latter, even after Roger became King of the Pirates and Whitebeard carried on as a pirate. Oden did, however, request that Roger allow Izou to take care of Whitebeard in his place. Izou served as a retainer for Wano Country daimyo Kozuki Oden, who later commanded the 16th division of the Whitebeard Pirates.
Why Didn't Whitebeard Attack the Beast Pirates to Get Retaliation for Oden's Death?
Because Wano was sealed off from the rest of One Piece's world, the Whitebeard Pirates only learned of Oden's death a few years after it happened. Of course, at that time, Marco and the others really did want to avenge Oden but did not take any action. As an Emperor, Whitebeard had lots of responsibilities on his shoulders. The lives of his entire crew -- and the people living in his territories and hometown -- were all depending on him to keep them safe. Whitebeard had two rules for his crew; one forbade them to kill anyone, while the other forbade them to take anyone's treasure.
Whitebeard not only followed these rules as if they were his life's motto but encouraged others in his crew to take the same path. It was a tough decision, but Whitebeard made a wise choice by not letting his emotions get the better of him. He knew that entering Wano would be a dangerous ordeal, and that two Yonko going against each other would be catastrophic.
The results of that war would not be in anyone's favor. Both sides, as well as Wano's civilians, would suffer tremendous casualties. Therefore, Whitebeard felt revenge was not worth risking the lives of his men and the people of Wano whom Oden had fought so hard to protect.