Rotom-W A --> A+
This is my first time nominating something, so this probably won't be perfect. Rotom-W is for me definetly A+ rank material. With only one weakness and solid defenses, Rotom-W can tank hits from so many things. Grass is not the best offensive typing to say the least, and essentially the only Grass-types to look out for are Seprerior and Venusaur. You can easily Volt Switch away from Venusaur, and carrying a counter or hard check to Serperior is not that hard (Mega Venusaur, Heatran, and Tornadus-T to name a few).
Rotom-Wash @ Leftovers
Ability: Levitate
EVs: 248 HP / 252 Def / 8 SpD
Bold Nature
- Volt Switch
- Will-O-Wisp
- Hydro Pump
- Pain Split
This is the basic defensive set, and is what I think is the best. Let me just list the S and A rank Pokemon I mean it walls (I've probably overlooked some): Azumarill, Heatran, Landorus-T, Bisharp, Talonflame, Tornadus-T, Gyarados (Not mega), Pinsir, Skarmory, Sand Rush Excadrill. That is quite a few Pokemon. My point here is that Rotom-W walls a ton of things, and there are almost no neutral hits that can OHKO it (A few exceptions like Specs Draco from Hydreigon, and Specs Hyper Beam from Sylveon). This little washing machine will as good as always get of something, if it's a Will-O-Wisp, a Volt Switch, or you can get your health back up with Pain Split. If you struggle with status like Toxic, easy enough, just run Rest or include a status absorber. With how often you Volt Switch, Toxic damage racking up probably won't be too much of a problem anyways. I am aware of that Rotom-W often can get worn down quickly by some powerful hits, but a Pain Split at the right time can quickly get you up to over 50 % HP, especially as Rotom-W has a low base HP. I don't really feel like Rotom-W needs any big amount of team support, you just need something that resists Grass and stops Earthquake from Mold Breaker Excadrill, and most teams fill these criterias already by simply having a Flying-type, as most Flying-types resist Grass. I don't feel like it really has that many big flaws, other than the fact that it could get worn down in not too many rounds if it has to take too many powerful hits, and does not get off a Pain Split or Rest. On the suspect ladder I have met it in actually like 40 % of all teams, and it is really anoying to deal with even though I have Mega Venusaur and Mold Breaker Excadrill to deal with it.
Volt Switch can be blocked by Ground-types but they often struggle if you predict the switch and go for Hydro Pump as shown by these calcs against Ground-types:
0 SpA Rotom-W Hydro Pump vs. 0 HP / 0 SpD Excadrill: 350-414 (96.9 - 114.6%) -- guaranteed OHKO after Stealth Rock
0 SpA Rotom-W Hydro Pump vs. 252 HP / 8 SpD Landorus-T: 294-348 (76.9 - 91%) -- 25% chance to OHKO after Stealth Rock (Defensive Landorus-T)
0 SpA Rotom-W Hydro Pump vs. 0 HP / 0 SpD Landorus-T: 296-350 (92.7 - 109.7%) -- guaranteed OHKO after Stealth Rock (Choice Scarf Landorus-T)
0 SpA Rotom-W Hydro Pump vs. 252 HP / 112 SpD Hippowdon: 282-332 (67.1 - 79%) -- guaranteed 2HKO after Leftovers recovery
0 SpA Rotom-W Hydro Pump vs. 0 HP / 0 SpD Mamoswine: 372-440 (103.6 - 122.5%) -- guaranteed OHKO
I don't really have anything else to add from my head, but I feel like I have kind of proven why Rotom-W should be A+. I don't really see what puts Rotom-W behind all the A+ Pokemon, and therefore I think it should rise to A+. To finish it off here are some defensive calcs:
252+ Atk Mold Breaker Excadrill Earthquake vs. 248 HP / 252+ Def Rotom-W: 254-300 (83.8 - 99%) -- guaranteed 2HKO after Leftovers recovery
252+ Atk Huge Power Azumarill Play Rough vs. 248 HP / 252+ Def Rotom-W: 123-145 (40.5 - 47.8%) -- guaranteed 3HKO after Leftovers recovery
252 Atk Landorus-T Superpower vs. 248 HP / 252+ Def Rotom-W: 97-115 (32 - 37.9%) -- 0.9% chance to 3HKO after Leftovers recovery
252+ Atk Choice Band Talonflame Brave Bird vs. 248 HP / 252+ Def Rotom-W: 81-96 (26.7 - 31.6%) -- 33.2% chance to 4HKO after Leftovers recovery
252+ Atk Bisharp Knock Off (97.5 BP) vs. 248 HP / 252+ Def Rotom-W: 117-138 (38.6 - 45.5%) -- guaranteed 3HKO after Stealth Rock and Leftovers recovery
252 Atk Mega Pinsir Close Combat vs. 248 HP / 252+ Def Rotom-W: 102-121 (33.6 - 39.9%) -- guaranteed 3HKO after Stealth Rock and Leftovers recovery
252+ Atk Life Orb Excadrill Rock Slide vs. 248 HP / 252+ Def Rotom-W: 83-99 (27.3 - 32.6%) -- guaranteed 4HKO after Stealth Rock and Leftovers recovery