Odd has a decent handful of arks, some of which are still ongoing. If I had to frame a general timeline in which the arks occurred it'd go something like:

Odd's birth, arrival in the Petriveil Region, and growing up with help from his dad/extended family

Odd reuniting with Giratina, learning the full scope of his powers/the responsibilities that come with them and him question what his existence is as a result

His high school/early college years where he befriends several other legendary connected people and becoming an agent for an interpol-adjacent organizations

His father dying, Odd entering a little bit of a downward spiral, but able to pick himself up enough in time to see through the climax of a conspiracy that that been developing over the past few years.

Odd after the climax, left alone after his closest friends are either dead, missing or comatose, and as a result some of his remaining extended family work together to sneak him out of Petriveil/cover it up from the organization he's in so he can get away for a while and have some time to reflect.

And his current Arc, manning his shop in Zirca as he sorts through who he is, everything that's happened in his past and what that means for him going forward

Jin actually has a few arcs. First was her original trip around Sinnoh as a teenager that was basically her being pulled into the plot of Platinum. Her next big arc was her finishing her aura guardian training in Kalos where she not only got her mega keystone, met her Riolu, but also was the first time she fell in love…and subsequently was the first time she got her heart broken. Then there was her trip to Hoenn and her meeting Mary…you can tell how that went. And while there are a lot more I could get into, the last one I want to mention is her becoming the warden to Regidrago and that involved a trip into the Crown tundra along with Mary and their daughter.

I'd say that her main story arcs are two: her Kalos and Galar arcs. She has some other arcs but those are kind of a way to set a basis for the two main arcs.

Kalos arc: Briar meets Lysandre, joins Team Flare and becomes the Commander. After a series of unfortunate events, Lysandre dies in Geosenge Town after the XY Protag stops his plans, and Briar ends up becoming the Boss of Team Flare briefly before disbanding the whole team. After this, Briar moves back to Unova to escape the Interpol agents who were still searching for Lysandre's allies.

Galar arc: Rose travels to Unova to search for a genius scientist he heard about in Galar that could help him with an important project of his. Although Briar had declared she was done with researches, his project interests her enough to accept working as a scientist again. This project would be known as Eternatus some years later. Her main arc.

Avian has a couple:
Sinnoh- 'Asshole child rival who never lost until he got the clapping of a lifetime that Broke Him and caused a massive spiral.'
Galar- 'The spiral never stops! Burnt out gifted kid is now a chronically depressed macro cosmos admin taken advantage of by his bosses and the company'
Sinnoh2- 'So Darkest Day happened, time to deal with my problems, recapture my old team and get into a bare knuckle fight with Lord Regigigas again.

Stahl and Arryn share the galarian champion cup from 30-ish years ago, falling in love and getting married. Stahl became a corporate exec, was not caught tied to eternatus and unfortunately believes Rose Was Right and whether it be a few years or decades we just need to try again.

As for Arryn: There's the fact she's a faller from Hisui and then after marriage became a lawyer who just so happens to frequently be reigning tower tycoon at various battle facilities across the world, participate in underground battles, go on expeditions to find legendary pokemon and about to start her next snippet of her take in Paldea to figure out what's up with Koraidon and if she can go back.