My last Ho-Oh set was pretty bad (I hid it. It was that bad) so I'm making a new one because I personally think Ho-Oh is the best Pokémon in Doubles Ubers right now. :P
Gen 8 Doubles Ubers
Ho-Oh @ Weakness Policy
EVs: 208 HP / 96 Atk / 204 Spe
- Sacred Fire / Flare Blitz
- Brave Bird
Offensive Tailwind setter and also a great Dynamax mon. Tailwind provides your team with valuable speed control, doubling their speed for 4 turns. This allows your ally Pokémon to outspeed stuff they usually can't, such as 16 speed Groudon, which can now outspeed Calyrex-S. Sacred Fire and Flare Blitz are Fire STAB options. Flare Blitz hits harder than Sacred Fire does, also having a better chance to OHKO Yveltal when used as Max Flare in sun. Sacred Fire, while less powerful, has the benefit of not causing recoil damage and also has that 50% chance to burn, but can also miss. Brave Bird is Flying STAB, which also boosts your team's speed further when used as Max Airstream, helping your team a lot if the opponent's team also has Tailwind up. Protect is near mandatory in Doubles (how many times have I said something like this in my moveset answers?? Actually don't answer that-). It allows you to scout for attacks while blocking all damage for a turn. Your ally can still act while Ho-Oh Protects. This can also stall out Dynamax / Tailwind / Trick Room turns and, against certain Dynamaxed mons, allow Ho-Oh's Weakness Policy to be more safely activated. With it’s Weakness Policy activated, Ho-Oh can be a terrifying Dynamax attacker, capable of snowballing through teams.
96 Attack EVs and an Adamant nature allow Ho-Oh to OHKO Zacian-C with Max Flare, coming off of Sacred Fire. With 204 Speed EVs, this Ho-Oh outspeeds the Ho-Oh in this sample team by 2 points of speed, allowing you to set up your own Tailwind before it (outsped it by 2 points instead of 1 so the remaining EVs woud make Ho-Oh's max HP odd, not even). The rest of the EVs are in HP. If you're using Flare Blitz over Sacred Fire, a different EV spread of 248 HP / 60 Atk / 200 Spe can be used, since it still speed creeps the Ho-Oh in the sample team shown, and still OHKOs Zacian-C with Max Flare.
Some good partners: (I'm not great at this sort of stuff)
Groudon provides automatic sun support for Ho-Oh, which allows Ho-Oh to pick up KOs that it wouldn't have otherwise. The sun also weakens Kyogre's attacks, allowing Ho-Oh to take them like their nothing. Groudon also appreciates Tailwind support from Ho-Oh, allowing it to outspeed Calyrex-S (and Zacian-C) with just 16 speed EVs.
252 SpA Mystic Water Kyogre Water Spout (150 BP) vs. 208 HP / 0 SpD Ho-Oh in Sun: 168-198 (41.4 - 48.8%) -- guaranteed 3HKO (lol)
and / or
These 2 mons can support Ho-Oh really well. Starting with Blastoise, Blastoise has access to Fake Out and Follow me, both of which help Ho-Oh set Tailwind up more easily and just keep Ho-Oh safer. It also has Aqua Jet and Flip turn, which activate Ho-Oh's Weakness Policy dealing little damage, and can break Focus Sashes (it also gets Yawn which stops opposing Dynamaxed mons in their tracks). Zamazanta-C can spam Coaching on Ho-Oh, making it much stronger and physically bulky with every use. It also blocks all spread moves with Wide Guard.