Perhaps when Ash meets his dad, his dad is on a very important mission. Ash decides to join him, and during this journey, they face many challenges together. His dad could teach Ash some new battle strategies that are different from what he has learned before. They might also encounter some rare and powerful Pokémon that they have to work together to either capture or overcome. This meeting could be a turning point in Ash's Pokémon - training journey, making him more mature and experienced.
They could develop a mentor - student relationship. His dad, being more experienced, could teach Ash advanced Pokémon training techniques. Ash, in turn, could show his dad his unique way of bonding with Pokémon, which his dad might not have seen before, thus deepening their connection.
In a fanfiction where Ash Ketchum meets the Avengers, there would be a huge clash of different worlds. Ash, being from the Pokémon universe, would bring his unique sense of adventure. The Avengers, on the other hand, are used to dealing with more technological and superhuman threats. Ash could introduce them to the concept of Pokémon, and perhaps some of the Avengers would be interested in having a Pokémon partner. For example, Tony Stark might see the potential in using Pokémon for his inventions. It would be a story full of surprises and new friendships.
Maybe a new, mysterious villain who has a grudge against Ash or wants to use his skills for their own evil purposes. This villain might be from a far - off region and has special powers that allow them to hypnotize people. They see Ash as a useful tool to carry out their plans in the Pokémon world.
His rival, Gary, could be a likely candidate. Gary has always been competitive with Ash, and in this fanfiction, his jealousy could reach a boiling point, causing him to betray Ash for his own gain, like trying to steal his Pokémon or get credit for his achievements.
Ash could become more confident and wise as a Dragon Master. His decision - making skills would improve as he deals with powerful and often unpredictable dragon Pokémon.
There could be a new character, a rival to Ash's dad from his younger days when he was an active Pokemon trainer. This rival could reappear in the fanfiction, causing some trouble or adding some drama to the story.
One of the greatest challenges could be taming the wild and powerful dragon Pokémon. Dragons are known for their fierce independence, and getting them to trust Ash would be no easy feat.