Here's my idea for the antagonist
Ennd the Alter Haxorus
Type: Holy/Ghost
Ennd has a strange power where no one except him can use attacks in his presence
Also other powers such as Zed being able to turn Alter and Mega Evolution are also void along with abilities
Basically his ability is Mold Breaker on steroids
Ennd has a goal
To invoke judgment onto all the evil Pokemon
But his image of evil is anyone who's killed, which involves some Pokemon that are too important to the world
Such as Avalon
So he like everyone else, wants to find Avalon, but for different reasons
But he's not unreasonable
If you can convince him that the good you've done outweighs the bad, he will spare you
But that is easier said than done
Ennd was a normal Haxorus once
He was living in his own region, but it was at war with Catharsis
He was a leading officer and was leading his troops, but was allowed to go home to his fiancee for a few days in the capital of the region
But it was during this time when Avalon attacked, wiping out Ennd's home in its entirety
Avalon with all his power was able to erase the incident along with any history of the region
But Ennd had somehow survived the attack, and became an Alter infused with the energy of Avalon's moves (hence his Holy/Ghost typing)
The war ended after that and Ennd was able to sneak into Catharsis and waited in hiding
When Avalon disappeared he took the opportunity, becoming a leader of one of the many 'gangs' that were popping up
He uses the gang to take out other gangs as a cover, but he's really trying to find out what happened to Avalon
Whether he can get his revenge, or if someone had already done it for him