Axemblaze

Maybe the Lady & Casanova double battle at Grand Hall works. They might not be there every day though.

Yeah, the Grand Hall Lady and Usually-Not-In-The-Overwold Casanova are your best bet there as much as they seem to utterly thrash me every time I try to challenge them.

I seem to recall an NPC in Reborn City saying that the energy from the Pledge moves lingers into the next round, thereby making their combos viable in Single Battles in theory. The only pokes that can learn two Pledges simultaneously are smeargle and silvally, though, and since I don't have either of those yet myself, I've yet to test it...