B+ -> A-
terrakion has proven to be a really great wallbreaker. like
p2 said, rock / fighting coverage + band terrakion's strength makes the thing very annoying to switch into... even for stuff that counters it on paper. it's capable of wearing stuff down really easily, especially on the typical bulky offensive builds that have been featuring terrakion lately. with pivots like rotom-w to bring it in, terrakion is capable of easily punching a hole
somewhere in your opponent's team. also, terrakion is definitely a good level above pretty much everything else in B+, and it's more on par with some of the A- rank stuff like mega heracross.
B -> B+
since hoopa-u's departure from the tier, there really haven't been many wallbreakers that are as pressuring as it was. band terrakion and other powerful choiced attackers sorta took its place on bulky offense builds that use slow pivots to make up for shitty speed tiers, but as far as stuff that doesn't need to be choice-locked to punch holes, you're mostly limited to megas like medicham, heracross, gardevoir, etc.. other than kyurem-b, nidoking is one of few non-mega wallbreakers in the tier that has a good amount of consistency. cbb's post highlighted a lot of the pros: good typing, resistances against certain forms of passive damage, and reliability. in addition to that, it's pretty obvious that nidoking has great coverage & power, and it gets to actually switch its moves!!! i don't think nidoking is a "hoopa replacement", but with hoopa gone, nidoking does stand out a bit more, and i definitely think it's on the same level as kyurem-b.
B -> B+
okay i get that everyone wants to be on the "hippowdon sucks" train nowadays, and while it has generally declined, i don't think it should be as low as B rank. while landorus-t and garchomp (even though tankchomp isn't as popular anymore) can fill the role of bulky / defensive ground, they don't totally outrank hippowdon. yes, hippowdon is passive as hell compared to those (and gliscor), but it provides more defensive consistency. hippo is capable of checking things like electrics, and (with a more specially defensive spread) mega diancie and tornadus-t, whereas bulkier lando-t / chomp sets really can't handle them. also, hippo can check both bisharp and zard-x, whereas chomp / lando-t can only check one each (bisharp for chomp, zard-x for lando-t). finally, hippo is just much more reliable in defensively checking stuff in general thanks to slack off lol. so yeah, hippo is super passive, but when you need to check a bunch of stuff on a balance or stall team and chomp / lando-t can't really do the job, hippo can easily. finally, i'm pretty sure hippo is a clear level above things like dragonite, politoed, and quagsire, and it fits in better with stuff like starmie, amoonguss, mew, etc..
B -> B-
i really don't think raikou should drop any further ;~;. yeah raikou isn't really as good as it once was, but it's still a pretty nice electric. the electrics as a whole have seemingly dropped in viability a bit, but that doesn't mean raikou needs to keep on going. it's simply a clear level above things like regular scizor, alomomola, mamoswine, mega garchomp, celebi....
there's a recurring theme of A rank's standards (as a whole like A+ / A / A-) that sorta tie in with the next few mons i'm gonna post about. it's pretty clear that the A ranks went through substantial shifts, with things like mega metagross and thundurus-i dropping from A+ to A-, keldeo and torn-t dropping from S to A+, mega sableye, talonflame, and mega lopunny dropping from A+ to A, etc.; however, things seem a bit jumbled up right now. what makes an S rank mon has been cleared up and is acceptable for sure, but A+ seems sorta different now... it went from being totally filled to now having very few mons. most of these mons in A+ are the glue / staple mons that really help to define the tier; whereas the less-defining mons that put a bunch of pressure on the tier have seemed to drop to A. since this hasn't really been cleared up since the revamp, i'm just gonna go with these observations while making / discussing these next few noms :3.
A- -> A
p2 already did a great job of summarizing this already, but to add to it... bisharp is about as good as weavile as an offensive dark; i'd say weavile is a little better, but not a whole rank better. while weavile is faster, equipped with ice / dark coverage, and more focused on immediate power, bisharp is a bit slower & bulkier with more focus on setting up to punch holes. bisharp also carries some neat traits that aren't comparable to anything weavile can do like defiant to pressure defog and a rock resistance meaning it doesn't get worn down like crazy between lorb and rocks (like weavile does). bisharp is capable of really posing a threat to both defensive builds and offensive builds (even though the sucker punch 50/50s are annoying v. offensive stuff it's still a huge threat), and it's a pretty huge pain in the butt to check in the builder.
A- -> A
mega latias is a hugeee deal atm. it's super nice on balanced and bulky offensive builds, it can check a bunch of important stuff like keldeo, electrics, volcanion, grasses, etc., and it has some variety to its sets. support, for example, can run thunder wave, defog, reflect type, refresh, a third attack, etc., and calm mind can go with reflect type or two attacks (with a variety of different attack combinations). there isn't really much to be said that hasn't been said; this thing checks the stuff you want a lati to check as efficiently as possible at the cost of some lowered offenses (compared to latios).
A -> A+
pursuit is huge as every other post in this thread mentions, and tyranitar is the premier pursuiter of the tier. tyranitar is just a great staple mon for variety of builds, capable of checking things like electrics, birds, the stuff you want to pursuit trap, etc., it has a variety of sets, and it provides sand support which is one of those things that'll pretty much always be great. like pursuit, sand is great, and tyranitar (literally!) fuels that. it's main 3 sets are all amazing: band, scarf, and support (chople berry usually), and it provides a ton of support to some top-tier metagame threats like keldeo and volcanion (with pursuit) and excadrill (with sand).
Infernal did a really good job of going into detail on all this stuff, so i suggest you just read her post about this lol.
A -> A+
sorta like with tyranitar, garchomp is one of the key staple mons of the tier, capable of checking a lot of important stuff both offensively and defensively while posing a major threat to teams with offensive sets like SD. yeah, tankchomp has fallen out of favor, and landorus-t is more or less the go-to ground at this point. sorta like with weavile / bisharp, i think lando-t is better than chomp, but not so much better that chomp is down in A rank because of it. also, nowadays i think the two are a bit different from one another; lando-t is more of a glue mon that handles stuff like sand, birds, and zard-x, whereas chomp is better as a more offensive mon. SD + rocks and salac berry + endure / sub + SD are capable of putting holes into a lot of the bulky offense teams we're seeing nowadays, and even with them running lando-t, SD chomp does a great job job of wearing it down quite a bit so something else on your team it had to check has a much easier time now. finally, i really think chomp is a level above everything in A rank except tyranitar and maybe heatran, and while it'd probably be a lower A+ rank mon, i think it fits in nicely.
there are a few other things i want to simply briefly comment on because i don't really have enough experience with them to write a bunch:
: this is really a question more than anything... why is this A-? i don't really see it on the same level as things like mega metagross, thundurus-i, serperior, jirachi, etc., so it seems kinda odd for it to be there.
: why is this thing ranked at all? i get that hoopa-u got banned, but we have other wallbreakers that "take its place" that are actually good.
: why is
this still ranked? there are much better grasses in the tier (mega venu, tang, amoong), and all roserade really has over them is toxic spikes, which isn't really worth it given how bad every other aspect of this thing is compared to those :x.