Ho-Oh has become a strong Defensive answer to many threats in Ubers such as Koraidon, Zacian-C, and Miraidon post-Tera. However, this is not impossible to wallbreak through. I’ll be using Ho-Oh’s typical Defensive Set to answer:
Ho-Oh @ Heavy-Duty Boots
Ability: Regenerator
Tera Type: Ground / Fairy / Water
EVs: 252 HP / 252 Def / 4 SpD
Impish Nature
- Sacred Fire
- Brave Bird
- Whirlwind / Will-O-Wisp
- Recover
My answers will be Mons that don’t need setup to at least 2HKO Ho-Oh. Not that set-up is good because of Whirlwind. This doesn’t include everything that can break through Ho-Oh but it includes the more relevant ones.
Pre-Tera:
Miraidon: Spec Miraidon can easily break through Ho-Oh pre Tera with STAB Electro
Drift.
252 SpA Choice Specs Hadron Engine Miraidon Electro Drift (133.3251953125 BP) vs. 252 HP / 4 SpD Ho-Oh in Electric Terrain: 794-936 (190.8 - 225%) -- guaranteed OHKO
Kyogre: Both Scarf and Spec sets can OHKO with Water Sprout intact
252 SpA Kyogre Water Spout (150 BP) vs. 252 HP / 4 SpD Ho-Oh in Rain: 560-660 (134.6 - 158.6%) -- guaranteed OHKO
Groudon: Offensive Variants can OHKO with Stone Edge.
252+ Atk Groudon Stone Edge vs. 252 HP / 252+ Def Ho-Oh: 412-488 (99 - 117.3%) -- 93.8% chance to OHKO
Koraidon: Ho-Oh gets 2HKOed by Banded Dragon Claw, although Koraidon must watch out for Brave Bird.
252 Atk Choice Band Orichalcum Pulse Koraidon Dragon Claw vs. 252 HP / 252+ Def Ho-Oh: 208-246 (50 - 59.1%) -- guaranteed 2HKO
Zacian-C: It can break through via Wild Charge, but must watch out for Sacred Fire.
+1 252 Atk Zacian-Crowned Wild Charge vs. 252 HP / 252+ Def Ho-Oh: 252-298 (60.5 - 71.6%) -- guaranteed 2HKO
Eternatus: Power Herb Meteor Beam can OHKO.
252+ SpA Eternatus Meteor Beam vs. 252 HP / 4 SpD Ho-Oh: 428-504 (102.8 - 121.1%) -- guaranteed OHKO
Post Tera
Ground:
Miraidon can break through via Draco Meteor, although Ho-Oh can play around this with Regenerator and swapping.
252 SpA Choice Specs Hadron Engine Miraidon Draco Meteor vs. 252 HP / 4 SpD Tera Ground Ho-Oh: 298-352 (71.6 - 84.6%) -- guaranteed 2HKO
Kyogre still OHKOs.
252 SpA Kyogre Water Spout (150 BP) vs. 252 HP / 4 SpD Tera Ground Ho-Oh in Rain: 560-660 (134.6 - 158.6%) -- guaranteed OHKO
Koraidon gets STAB to hit harder.
252 Atk Choice Band Orichalcum Pulse Koraidon Flare Blitz vs. 252 HP / 252+ Def Tera Ground Ho-Oh in Sun: 311-367 (74.7 - 88.2%) -- guaranteed 2HKO
Fairy:
Spec Kyogre can OHKO.
252+ SpA Choice Specs Kyogre Water Spout (150 BP) vs. 252 HP / 4 SpD Tera Fairy Ho-Oh in Rain: 459-541 (110.3 - 130%) -- guaranteed OHKO
Miraidon can still break through via Electro Drift.
252 SpA Choice Specs Hadron Engine Miraidon Electro Drift vs. 252 HP / 4 SpD Tera Fairy Ho-Oh in Electric Terrain: 298-352 (71.6 - 84.6%) -- guaranteed 2HKO
Koraidon can still break through via Flare Blitz but still needs to be mindful of Brave Bird.
252 Atk Choice Band Orichalcum Pulse Koraidon Flare Blitz vs. 252 HP / 252+ Def Tera Fairy Ho-Oh in Sun: 311-367 (74.7 - 88.2%) -- guaranteed 2HKO
Zacian-C can OHKO with Behemoth Bash.
+1 252 Atk Zacian-Crowned Behemoth Blade vs. 252 HP / 252+ Def Tera Fairy Ho-Oh: 422-498 (101.4 - 119.7%) -- guaranteed OHKO
Necrozma Dusk Mane can do a decent amount but has to watch for Sacred Fire.
252+ Atk Necrozma-Dusk-Mane Sunsteel Strike vs. 252 HP / 252+ Def Tera Fairy Ho-Oh: 320-378 (76.9 - 90.8%) -- guaranteed 2HKO
Water:
Miraidon OHKOs.
252 SpA Choice Specs Hadron Engine Miraidon Electro Drift (133.3251953125 BP) vs. 252 HP / 4 SpD Tera Water Ho-Oh in Electric Terrain: 794-936 (190.8 - 225%) -- guaranteed OHKO
Zacian-C breaks through.
+1 252 Atk Zacian-Crowned Wild Charge vs. 252 HP / 252+ Def Tera Water Ho-Oh: 252-298 (60.5 - 71.6%) -- guaranteed 2HKO
Koraidon’s Low Kick is no longer resisted and punches holes.
252 Atk Choice Band Orichalcum Pulse Koraidon Low Kick (100 BP) vs. 252 HP / 252+ Def Tera Water Ho-Oh: 259-306 (62.2 - 73.5%) -- guaranteed 2HKO
Hope this helps!