Came up with something as a result of some discussion on discord. Behold the one true counter:
Blissey @ Leftovers / Mago Berry ( / Icium Z / Firium Z )
Ability: Serene Grace
EVs: 252 HP / 4 SpA / 252 SpD
Calm Nature
- Calm Mind
- Ice Beam
- Softboiled
- Substitute / Flamethrower / Toxic / Minimize / Thunderbolt
Blissey/Chansey seemed like really good checks in the first few days of USUM until we realised that +6 Z Draco bops them and Naga can very easily boost to that. But what if Blissey has SpD boosts? That's where this innovative set comes into play.
Full special bulk Blissey can switch into boosted Naga and start boosting right in front of it.
+2 236 SpA Naganadel Devastating Drake (195 BP) vs. 252 HP / 252+ SpD Blissey: 190-225 (52.4 - 62.1%) -- 98.8% chance to 2HKO after Leftovers recovery
+2 236 SpA Naganadel Draco Meteor vs. +1 252 HP / 252+ SpD Blissey: 84-100 (23.2 - 27.6%) -- possible 5HKO after Leftovers recovery
+4 236 SpA Naganadel Devastating Drake (195 BP) vs. +1 252 HP / 252+ SpD Blissey: 190-225 (52.4 - 62.1%) -- 98.8% chance to 2HKO after Leftovers recovery
+4 236 SpA Naganadel Draco Meteor vs. +2 252 HP / 252+ SpD Blissey: 96-114 (26.5 - 31.4%) -- 19.3% chance to 4HKO after Leftovers recovery
+6 236 SpA Naganadel Devastating Drake (195 BP) vs. +2 252 HP / 252+ SpD Blissey: 190-225 (52.4 - 62.1%) -- 98.8% chance to 2HKO after Leftovers recovery
+6 236 SpA Naganadel Draco Meteor vs. +3 252 HP / 252+ SpD Blissey: 102-121 (28.1 - 33.4%) -- 94.3% chance to 4HKO after Leftovers recovery
+2 0 SpA Blissey Ice Beam vs. 20 HP / 0 SpD Naganadel: 138-164 (91.3 - 108.6%) -- 50% chance to OHKO
0 SpA Blissey Subzero Slammer (175 BP) vs. 20 HP / 0 SpD Naganadel: 136-160 (90 - 105.9%) -- 37.5% chance to OHKO
Lefties / Mago doesn't really matter. Lefties is the traditional item but Mago might actually be better.
Sub is cool with Mago because it activates the berry after taking a Z move and puts you around 60% with a healthy Sub which makes setting up on Naga even easier, but it's also good for scouting switches. Flamethrower hurts Ferrothorn. Toxic hurts switches. Minimize is Minimize. Thunderbolt hurts Gyarados switch ins.
Unfortunately you have to use special bulk on this set so physical attackers bop it. I considered Maranga Berry with a bold spread but the calcs were kinda bad still. Icium Z is an option for quick damage. Same with Firium on Ferro.
There was talk of a Z Snatch Blissey which sounded really funny (+2 speed and steals the Nasty Plot) but relies on the Naga boosting and doesn't outspeed if the Naga got a kill so I decided against nominating it. There were also a bunch of other mons thrown around in the chat so I'm looking forward to seeing what everyone else posts. Ttar / Heatran work but I wanna see AV Regice / banded Mamoswine etc lol.