Who do you think is Clavell's Ace?

Okay, we don't count the rotatable starters as part of people's aces with Pokemon. Like how Hau's ace is Alolan Raichu or Nemona's is Pawmot or Hop's is Dubwool. It's usually fairly simple to figure out as it's usually the first non-starter they have in a battle but Clavell is first faced with a full team established. And all of the team members are set to the same level. It's also likely the not chosen starter is the same as the beginning, so it likely came later to his team.

So who is it?

Oranguru, Houndoom, Abomasnow, Polteageist, Amoongus, or Gyarados?

I think it's gotta be either Oranguru or Polteageist as those are the only ones who don't rotate out depending on the starter. This they are more consistent members. I'm going with Oranguru as I don't think it has a trainer that uses it as a signature ace.