Welp, time for another long string of nominations:
Shuckle: A=>B (Bug)
The main reason Shuckle should be brought down is because a lot of its roles are done better. Galvantula is the superior Sticky Web setter due to its great part Electric typing and an actual offensive presence with helpful coverage. Armaldo is better as a Stealth Rocker and Fire sponge due to actually being able to offensively threaten the Fire types it sponges. It shares Shuckle's Knock Off utility, while also offering further utility in Rapid Spin. Forretress serves as a better Stealth Rocker on more balanced teams due to having further utility in Rapid Spin and Volt Switch, while also checking the insane threat that is Terrakion. Shuckle's still a decent choice, but the fact that most of its roles can be performed better warrants its drop to B rank.
Mega Sharpedo: A=>S (Dark)
Similarly to how Mega Sableye is essential to balanced Dark teams, Mega Sharpedo is essential to offensive Dark teams. Thanks to its pre-Mega ability Speed Boost coupled with its post-Mega ability Strong Jaw, Mega Sharpedo is without a doubt one of Dark's best late-game cleaners. It has great coverage with Ice Fang and Psychic Fangs, capable of tearing through a wide range of threats like Keldeo, Heracross, Garchomp, and Dragonite, as well as potentially sweeping Poison once Mega Venusaur and Toxapex have been weakened. While it is a physical powerhouse, it can also run mixed sets effectively with Hydro Pump, allowing it to beat Skarmory, Hippowdon, and Mega Steelix. Mega Sharpedo is incredibly important to offensive Dark teams, and is definitely worth returning to S rank.
Goodra: C=>B (Dragon)
I am aware that this nomination was made earlier, but I think Goodra should definitely be moved up on Dragon. With 150 Special Defense with an Assault Vest, Goodra is one of Dragon's best switch-ins to special attackers. Here are some calcs demonstrating its amazing special bulk:
252 SpA Tapu Koko Dazzling Gleam vs. 248 HP / 0 SpD Assault Vest Goodra: 102-120 (26.6 - 31.3%) -- guaranteed 4HKO
0 SpA Tapu Fini Moonblast vs. 248 HP / 0 SpD Assault Vest Goodra: 92-110 (24 - 28.7%) -- 96.9% chance to 4HKO
252 SpA Life Orb Sheer Force Landorus Earth Power vs. 248 HP / 0 SpD Assault Vest Goodra: 107-126 (27.9 - 32.8%) -- guaranteed 4HKO
252 SpA Latios Draco Meteor vs. 248 HP / 0 SpD Assault Vest Goodra: 200-236 (52.2 - 61.6%) -- guaranteed 2HKO
In addition to its amazing special bulk, it also has a strong offensive presence with fantastic moves like Sludge Bomb, Flamethrower, Ice Beam, and Earthquake, allowing it to deal with the threats listed in the calcs, as well as Hippowdon, Heatran, Gliscor, and Ferrothorn. It has amazing abilities in Sap Sipper and Gooey. Gooey can be especially helpful when a wallbreaker like Hydreigon or Dragonite needs to outspeed a physical sweeper, and Sap Sipper is great for switching into Leech Seeds from Ferrothorn and Celesteela. Due to Goodra's versatile offensive and defensive presence, it is definitely worthy of at least B rank.
Golurk: B=>C (Ghost)
The introduction of Alolan Marowak has left Golurk extremely outclassed in terms of having far more power and a much better defensive typing. While Golurk does have nice Fighting coverage, Doublade has this while also having a better defensive typing, Swords Dance, and far better physical bulk. Doublade also outclasses it as a Rock resist. As a suicide lead, it has a very poor Speed stat, leaving it outsped by just about every Taunt user and being easily revenge killed without its Focus Sash. Since Ghost usually has a tough time keeping hazards away, even with Mega Sableye, Golurk will often find itself unable to check threats. Right now, Golurk is a pretty niche pick and should be dropped to C rank.
Mega Steelix: D=>B (Ground)
Mega Steelix has proven itself to be incredibly helpful for Ground teams due to being the only switch in to Choice Scarf Tapu Bulu that the type has access to. In addition to Tapu Bulu, it can also switch into threats like Breloom and Kyurem-Black and do major damage to them with Heavy Slam. With its great defensive typing, it can serve as an alternative Stealth Rocker for Sand Ground teams, freeing Hippowdon's last moveslot for something like Toxic. While it does have certain flaws holding it back, such as having no reliable sustain and having some of its roles done better by Hippowdon, it still has enough beneficial traits to warrant a spot on B rank.
Aurorus: B=>C (Ice)
Back in ORAS, Aurorus was definitely one of the best Snow Warning Pokemon due to its nice utility with Stealth Rock, Encore, and Thunder Wave. But now, Alolan Ninetales has solidified itself as the superior Snow Warning Pokemon due to its higher Speed, better offensive typing, and more valuable utility in Aurora Veil. As a Stealth Rocker, Piloswine can sponge Fire type attacks better while also having important utility in Roar, and Mamoswine has a far better offensive presence, as well as being able to check a large amount of threats with Endeavor + Ice Shard. There isn't a lot justifying Aurorus on Ice teams due to how outclassed it is, which is why I think it should be lowered to C rank.
Mega Alakazam: A=>S (Psychic)
With Mega Medicham being banned, Mega Alakazam has returned as Psychic's best Mega Evolution. With Trace, it can not only function as an amazing speed control option, but it can also be helpful in safely switching into Pokemon like Heatran and Thundurus-Therian when they try to go for Fire and Electric type attacks respectively. With 150 Speed, it can outspeed a large portion of the unboosted metagame, as well as certain Choice Scarf Pokemon like Mamoswine and Xurkitree. It functions as a fantastic wallbreaker with its 175 Special Attack, as well as having helpful utility in Substitute and Encore. While Sash-Counter Alakazam is still a fantastic asset capable of checking a wide range of physical threats, Mega Alakazam is near essential on offensive Psychic teams and is definitely deserving of S rank.
Seismitoad: B=>A (Water)
Seismitoad is essential to Swift Swim Water teams due to being the best Stealth Rocker the archetype has, as well as having an important Electric immunity. With Sludge Wave, it can serve as an effective check to threats like Tapu Bulu, Tapu Fini, and Clefable. In rain, it hits up to 494 Speed, outspeeding many threatening Choice Scarf Pokemon like Victini and Jirachi. Seismitoad is absolutely vital to Swift Swim Water and it is fully deserving of A rank.