S Rank
Araquanid - Massively helpful mon for Bug's most grueling match ups and generally good specially defensive presence on the type that brings tons of utility and firepower to the table in the form of Webs, anti-leading, specially defensive walling and Adaptabilty boosted water attacks. While definitely lacking in the longevity deparment and perhaps too slow for its own good when discussing offensive sets, and sometimes defensive ones as well, Araquanid is an incredibly versatile mon that feels like a necessary presence in any semi decent Bug team not all out hyper offense, and even then it has a place in those as well
Kleavor - Great scarfer, great anti fire, flying and mirror tech and quite powerful for its speed tier and downright ridiculous STABs when Sharpness is taken into account, all things considered. Has been a vital part of Bug for well over half a year and I don't think that will be changing any time soon.
Volcarona - While you could make an argument for this mon not being as good anymore, I'd only say that's because of a weird mix of recency bias and the latest meta changes; while perhaps not as meta defining, that's if only because of how warping this mon presence can be with its jawdropping variety of sets (taking offense, Z move and defensive sets into account) and how it only feels that way because of the fact the meta has forced itself to be able to deal with such a monster of a mon. Volcarona is still one of the most terrifying mons to fight against, and it probably will always be, no Bug team should not use it.
A+ Rank
Buzzwole - While the Scarf sets are arguably outclassed by Kleavor, even though they are still perfectly functional, Buzzwole is still the best Bug/Fighting type, and I personally believe its bulky sweeping sets and stall killer with Taunt, Substitute and Bulk Up are madly underrated. Great mon, incredibly helpful in the Steel, Dark, Poison and Fighting match ups, even if somewhat hard to fit nowadays. While I initially would have ranked it as A Rank, I believe its sheer versatility, ability to create a Double Scarfer core together with Kleavor and wonderful defensive presence in the context of Bug overall make it a somewhat underrated option nowadays.
Pinsir-Mega - Best mega for the type and Fighting and Grass winner, excellent wall breaker, decently bulky and great priority couple to Scizor; same as Volcarona, it can use either Close Combat or Earthquake to selectively pick what match ups it wants to win. While the speed tier is... not the best, with webs supports it is a truly frightening mon to face against.
Scizor - Versatily incarnated, it can pull almost any set it wants (Band, Physically defensive, Utility, Sweeping with SD and Trailblaze) with surprising excellency and it just wins against Ice and Rock unless they run Shell Smash Cloyster or H-Arcanine, respectively, and even then Bug still has a fair advantage. While not intricately necessary, this mon is still as wonderful as it has always been.
A Rank
Forretress - I would make an argument for it being B Rank, but Forretress is still rather good as hazard removal and general physical wall, with Volt Switch being a great tool for it and through Gyro Ball, Body Press and not too shabby of an Attack stat making it not too passive, even though the opportunity cost of not using Scizor might be a bit too much. Even then, repeating Bug / Steel as a type is not the worst thing in the world.
Galvantula - Not powerful at all even through Compound Eyes Thunder and not nearly fast enough to compensate, Galvantula is still quite fine on the department of a second special attacker for bug and its Web support and lead sets are still as valuable as ever.
Scizor-Mega - Actually really good, but you'd definitely prefer either Mega Pinsir or Base Scizor in the vast majority of situations.
Ribombee - Somewhat goated of a mon, actually: good at a minimum at anything it wants to do, be it remover, general utility, sweeper with QD or even as a Speced "wallbreaker", and a genuinely excellent speed tier make it a valuable addition to any Bug team that can afford to run it.
Vikavolt - Stabilizer of the Electric, Water and Flying and great helper in the Ground and Steel ones, I believe of Vikavolt to be the best of the non-Volcarona special attackers, it greatly punishes more passive teams and while the abymal speed tier makes it funkier to use against offense, its decent bulk actually makes it a versatile, decent mon in any match up not called Rock or Fire, where it can still do some excellent wallbreaking against the slower, bulkier mons of either type.
B Rank
Armaldo - Good at what it wants to do, but you have no actual reason to use it; Bug / Rock is not a good defensive type, you don't want to stack it with Kleavor and you
want to use Kleavor, and removal is actually done better by Forretress, Scizor, Ribombee or, hell, even the dumbass set that is Defog Kleavor. Fine, but throughly outclassed and relying in Stone Miss sucks.
Golisopod - Probably the mon with the most untapped potential of the entire list and with and incredibly high skill ceiling, Golisopod has great typing, excellent priority, peculiar ability and a truly expansive movepool. I believe it can actually be really good, but I'm not too sure about it.
Heracross - Same as Armaldo, just a worse Buzzwole, good if you want to use it and unique on regards to Guts.
Heracross-Mega - This mon is good and definitely can pull its weight, but it needs far more support than either Scizor or Pinsir and the opportunity cost of not using either of those two is... really bad, sadly. Underexplored, perhaps as good as Scizor-Mega, not sure.
Lokix - Cookie Cutter good mon, helps in Dark, Electric, Psychic and against more defensive types, its priority does wonder and it can be a wallbreaker extraordinaire. Can understand it's hard to fit but that doesn't warrant the C Rank, personally.
C Rank
All of these are good and can pull somewhat unique niches, but are needlessly outclassed
Durant - Good bander, really powerful, yet inconsistent and outclassed.
Frosmoth - Bad speed tier, QD is always good and its ability is great, yet it is too inconsistent and the lack of HP really hurts.
Scolipede - The probably best Z Move user in bug not named Volcarona, lacking in power but can get out of hand.
Slither Wing - Meh, cookie cutter mediocrity that's not awful.
D Rank
Centiskorch - Fire immunity can come in handy and Fire Lash is a great move, not really good otherwise.
Rabsca - I wish it had Teleport; GREAT coverage, though.
Yanmega - While it was UnRanked a while ago, I feel it is a... decent to mediocre option for a Special Attacker, at the very least deserving of a mention.