Water Tera Azumarill can solo Emboar intimidateless. Rerolling for AI here was probably the toughest part, though losing runs to random crits right after fully setting up is disheartening as well. I settled for Sylveon because Charm doesn't really help in the worst part of the fight.
Emboar is rather finicky with its choice of using Flare Blitz on Azumarill as noted before, so I actually think tera Water could be better than Fairy here with all other things equal, especially if you rig for Intimidate/Gardevoir to make the earlygame more consistent since it's the same either way before you tera, just because Liquidation is better than Play Rough and I don't want to give Emboar any more reasons to Flare Blitz. I think Azumarill at least has a more consistent endgame than it sounds like for Garchomp while also not having to use a DLC TM. In general I feel like the idea of defensive typing and hitting weaknesses is a pretty overrated aspect, even in prerelease with non STAB 50 BP Trailblaze being considered as a threat.
In general the strategy is similar to the main Azumarill one but with Liquidation instead of Play Rough which can lower defense and is 100% accurate. Another main difference here is that I tried Chilling Water to lower variance compared to Mud-Slap as well. Also my Jolly Azumarill speed ties Emboar, so the opening is a bit more unreliable with a coinflip (though that's also avoidable by moving 4 EVs to Speed or not being Jolly) and I can't use Belly Drum T1 like Marill, but I can get a Chilling Water in early that works, though I still face chance of death from Wild Charge if it goes first. Sometimes I can get multiple Chilling Waters if Emboar is generous with Flare Blitzes, though that ends up sacrificing the cheers which is a pain in the long run to outpace Emboar's offense.
0+ Atk Reckless Tera Electric Emboar Wild Charge vs. 84 HP / 56 Def Azumarill: 342-404 (94.4 - 111.6%) -- 68.8% chance to OHKO
0+ Atk Reckless Tera Electric Emboar Wild Charge vs. 252 HP / 0 Def Azumarill: 368-434 (91 - 107.4%) -- 43.8% chance to OHKO
0+ Atk Reckless Tera Electric Emboar Wild Charge vs. 0 HP / 252 Def Azumarill: 278-330 (81.5 - 96.7%) -- guaranteed 2HKO
In this attempt I got very lucky with Emboar's choice of Flare Blitz spamming most of the time. Emboar actually got to -3 Attack turn 1 thanks to Sylveon's Charm, but it still managed to kill me thanks to getting a crit, so I guess that balances out my luck. I also mashed into Liquidation on that turn which didn't really matter and I probably could have hit an ally instead to heal less from Shell Bell.
I ended up setting 3 Defense Curls again, but only settled for one Chilling Water to tera. Bellibolt's Mud Shot breaks the speed tie and makes things more reliable overall. Flare Blitzes only did like 40-30 damage, though one burned during setup that I heal cheered to full with, and a Wild Charge ended up doing 68 damage after +3, so I felt safe to Belly Drum after that.
-1 0+ Atk Reckless Tera Electric Emboar Wild Charge vs. +3 84 HP / 56 Def Azumarill through Def Cheer: 62-74 (17.1 - 20.4%) -- possible 5HKO
Here you can see that Sylveon did not really help me out with a Charm after the shield break/debuff because I used a Chilling Water after the shield break to mitigate Bulk Up's impact. The worst damage I took was from a double +1 Wild Charge in the lategame right after the bulk ups from full HP, which still only 2HKOs without a crit to take me down to 60, and I was able to finish right after with a lucky crit.
+1 0+ Atk Reckless Tera Electric Emboar Wild Charge vs. +3 84 HP / 56 Def Azumarill through Def Cheer: 138-164 (38.1 - 45.3%) -- guaranteed 3HKO
EDIT: I actually should have lost this if Emboar was smart, but it used Flare Blitz on me and left me at 6 HP. So that's another pro of resisting Flare Blitz.