Another possibility is Heimdall. As the all - seeing guardian of the Bifrost, he would be aware of Odin's situation from the start. He could be the one trying to piece together what happened to Odin and prevent any disasters that might occur as a result of Odin's wipe. His unique abilities and loyalty to Asgard would make him a strong candidate for the main character.
In the 'odin gets wiped fanfiction', it might be that Odin has his powers wiped instead. This would change the power dynamics in the story. He would no longer be the all - powerful figure. His allies may have to step up and protect him, and his enemies might see this as an opportunity to attack. It could also be a chance for Odin to grow in a different way, learning to rely on other skills or relationships rather than just his godly powers.
He might become withdrawn at first. Since he's used to being in control and having a certain dynamic in their relationship, Bella's anger could shock him into pulling back. He could go off on his own for a while to think about what he did wrong.
Another possibility is a jealous rival. Maybe there's someone who is jealous of Gohan's power or his relationship with certain characters. This rival could do things to annoy Gohan and push him to the edge of his temper.
A new player on an opposing team could be the cause. This new player might be overly cocky and disrespectful towards Kuroko during a game. They could constantly taunt him about his lack of presence, which finally gets on Kuroko's nerves and makes him mad.
It could be Vegeta. Maybe Vegeta does something really underhanded like stealing Goku's senzu beans or trying to take all the credit for a victory that Goku also contributed to. Goku, being a fair - minded person, would get angry at such behavior.
One of his friends could be the cause, accidentally. Maybe a friend makes a deal with a shady character without realizing the consequences. This deal ends up putting everyone in danger, and Yami gets mad at his friend's naivete and the mess they've created.
In a Naruto Gets Odin's Eye fanfiction, there could be a plot where Naruto's world is somehow merged with the world of Norse mythology. The acquisition of Odin's eye could be a key factor in this merge. Naruto could use the eye to communicate with the Norse gods and gain their support in battles against his foes. This could also introduce new villains from Norse mythology. His friends in Konoha would be both amazed and a bit intimidated by his new power. Naruto would have to learn to control the power of Odin's eye quickly to prevent it from causing chaos in his village.
Definitely Doofenshmirtz. He could mess with one of Phineas and Ferb's inventions in a way that really ticks Phineas off. Like he might use one of his -inator devices to turn their amazing flying machine into a pile of junk. Phineas would be furious and would then set out to fix it and get revenge on Doofenshmirtz.
It could be his rival. Rivals in Yu - Gi - Oh are always trying to one - up each other. If his rival manages to steal a rare card that Zane has been eyeing, or if the rival taunts Zane about a recent defeat, that would surely make Zane mad.