Since the meta has a settled down since Cacturne's buff and Komo-o's arrival, I believe we can talk about the Pokémon that need a buff just like Cacturne did.
I) The worst ones
Porygon-Z suffers from its shitty typing which let it easily weakened by hazards damages. That coupled with its average bulk leaves PZ with a trash staying power. Bug is also a really poor offensive typing which is resisted by most wall/tank such as Nihilego, Audino-M, Forretress, Flygon, Celesteela and to an extent Druddigon, Flaafy and Toucannon. From rank S to A- there is only 2 bug weak Pokémon (Meganium and Unown) which means that Porygon-Z will often suffers to pressurize the opposing team. Porygon will also struggle to set-up with Nasty Plot, Agility or Conversion. It suffers from 4mss since it needs STAB Bug Buzz, Psyshock for Nihilego, Ice Beam for Flygon, Drudiggon, Flaafy and Toucannon, Hidden Power Fire for Forretress, Nasty Plot for Audino, Lanturn and Celesteela and Agility/Trick Room for offense.
There is no real reason not to use a fast special attacker such as Raichu, Unown or Ninjask over Porygon-Z.
What can be made?
There are several ways to make PZ better since it needs to find a niche in the current metagame. Porygon-Z needs to get an unique niche that no other Pokémon can perform.
Examples:
New ability: Speed Boost as an ability to make it a better cleaner, offensive threat while still struggling with coverage, Protean to let it unwallable but still struggling with offense. An ORAS Gale Wings clone for Bug-move can turn it into a dangerous revenge killer and cleaner with powerfull and fast Bug Buzz.
Stats buff: Bulk or Speed.
Movepool: U-Turn, Heal Order (if Gale Wings), Bug-type Topsy Turvy (if Gale Wings), Fire-type coverage, Quiver Dance
Raticate-A struggles to find a place in the current metagame because Gravity is worst than other weather condition/terrains. Indeed unlike Cacturne, Ninjask or Genesect, Raticate-A is useless without its weather with a pitifull 71 base Attack and 77 base Speed. Removing Gravity isn't really hard since M-Pert and Komo-o can played outside of Rain and Sand-team, but also revenge killing Raticate under Gravity isn't hard because of it's slowness.
It's hard to justify using Gravity over other weather conditions, and to run CeleRat over XurkGene, JaskPert or KomTurne.
What can be made?
We need to make Gravity more attractfull, this can be made by buffing Extreme Bulk and Faticate Speed. Raticate needs to not be a deadweight outside of Gravity and not being easily revenge killed under Gravity.
Vikavolt might be just underexplored but I feel like it's really underwhelming. In fact it struggles to break through Nihilego, Lanturn, Swampert, Rhydon and Kommo-o which are top tiers threats. Technician boosted Hidden Power are very potent but Vikavolt needs Grass to hit Swampert, Rhydon and Lanturn, Ice to hit Kommoo and Fire to hit Forretress which leaves it with a 4mss. It can't realiably click Volt-Switch because every Ground-type punishes it because of its quad Ground weakness.
Vikavolt suffers from its lackluster movepool and to an extent from its bad typing.
What can be made?
Vikavolt needs to get an other coverage than Hidden Powern, Bug and Steel. Giving it Energy Ball back or an Ice-move would let it be far better. Another option I can imagine, is giving it Power Gem and an ability that allows it to bypass Electric immunity (1k arrows clone).
I want be to long with this one.
Lycanroc is a glass cannon that lacks speed. It gets outsped by Kommo-o, Unown, Sharpedo, Ninjask, Raichu and Offensive Nihilego, and it doesn't have any way to touch them because it doesn't have any priority.
What can be made?
Lycanroc needs either strong priorities or a better Speed Tier. But i believe a mix of both is the good way to go.
II) The bad ones
After a few cheap damages from U-Turn/Volt Switch it's very hard to set up Musharna, add to this that it struggles with the two of the three most common Special Wall. It's also a Fairy-type that can't handle Kommo-o which kind of sucks. I suggest to slightly increase Mush's bulk.
The number of Pokémon that Trapinch can trap is very low because a lot of top tiers are ungrounded, Ghost-types or carries U-Turn. It's also a poor Electric-check because it takes a lot from Raichu's Ice Beam and Xurk's Energy Ball. I believe that Trapinch needs a buff in SpD and let Arena Trap trap Ghost-types.
Flaafy has an incredible bulk but is easily chipped because of no passive recovery, SR weakness and relying on Wish to get its health back. I believe that just giving Flaafy Roost and a Flying-type Giga Drain clone will solve all its problems.
Cloyster is hard to use in a team because its needs several boost to become threatening, is easily revenge killed (but like really easily) and is walled by Lanturn and Forretress which are really common. I believe that giving Cloyster Ice-coverage back isn't a bad idea, but also and especially turn Vicious Mockery into a Psycho Boost clone.
That was just some of my thoughts.