Summarizing the big feats that would affect tiering, starting with the Destroyer:
The Destroyer being stated to be
ripping the planet apart,
twice during the final period of Borderlands 3 (which can be seen and felt in game). Pandora is a giant man-made planet
built by the Eridians with an
upper mantle made entirely out of Eridium. Pandora was made specifically to cage the Destroyer and it is
noted that even the Eridians who's
reach can "pluck stars from across the void" ,
built the moo and the Vault of the Serpent (which
contains a large amount of stars and a su), took centuries to build Pandora (Which goes to show how dangerous the Destroyer is to the Eridians). This would get rid of any arguments that would try to claim The Destroyer isn't anything above High 7-C because he can't escape Pandora...but there's more. The Destroyer is
stated to literally eat starsand this is backed up again by the
Eridian writings which states "
even as stars in the sky above began to wink out" when refering to Eridian's building Pandora while the Destroyer is consuming more and more stars. Tyreen's goal also aligns with these statements as well. She wants to absorb the Destroyer and literally consume stars until she is literally the only star in the sky. Although something from BL TPS seems to contradict the Destroyer having this kind of power.
In The Pre-Sequel, Handsome Jack uses the Destroyer's eye as a laser and amplifies its power 10 fold by using Slag. Although this contraption is stated to be able to destroy Elpis (the moon), it seemingly contradicts the statements regarding the Destroyer eating stars in BL3 because it would mean the eye can only perform multi-continental to moon level feat only when it's boosted to 10x it's normal destructiveness by slag. But this is easily be explained by the Destroyer's eye output just not being comparable in power to it's full self which we know makes up a large portion of Pandora and is likely larger than Elpis. This also leads to the next character I would like to discuss which is Lilith.
Lilith after finally getting her power back from Tyreen and having not absorb any Eridium,
pushed the giant ass moon Elpis away from Pandora albeit possibly at the cost of her life.
Here's where Elpis was originally,
here's how close Elpis was to Pandora
before Troy made it come closer and
here's how far Lilith pushed the moon back. If you have a keen eye, than you can see that Lilith pushed Elpis back to it's original position. Now you may ask "Why does this matter? Lilith is implied to have died from doing this." and you would be correct but keep in mind what I said before, this is a Lilith who just got her powers back from Tyreen and hasn't absorbed any Eridium meaning this would scale to Tyreen and Troy. Now you might also ask "How does this scale to Tyreen and Troy? They aren't Lilith!" and to answer that is easy. Tyreen upon first appearing dominated Lilith and absorbed her powers, along with absorbing numerous amounts of cultists, vault monsters, eridium and the Destroyer, it would be hard to prove that Tyreen doesn't scale to this feat but she wouldn't be the only one who scales here, Troy and mid-game BL3 Vault Hunters would also scale of course. Now onto the next feat which hopefully proves the consistency of this feat.
To make this simple, Troy
phaselocks Elpis and brings it closer to Pandora and charge it with his power. This feat was initially done with Eridium as his supply making it difficult to sell as a feat but later on in the mission the VHs cut off Troy's supply of Eridium and so Troy began using Tyreen as the energy source to charge Elpis which is not just a moon but the Vault Key for Pandora that was created by the Eridians that can open Pandora and unleash the Destroyer. This means it makes sense that Troy used outside power sources to charge the moon and it doesn't contradict Lilith's feat but rather helps it, nor does it contradict the scaling that would arise from it. Which would be:
At least 5-C Tyreen and Troy (Should be far stronger than Lilith who performed that moon feat without Eridium and right after her siren powers returned)
At least 5-C Mid-Game BL3 VHs (Defeated Troy who absorbed large amounts of eridium and Tyreen's powers during their fight)
At least 5-B, likely 4-C for the Destroyer (Far stronger than Siren's such as Lilith, Tyreen and Troy who could perform (insert those moon feats here) and was repeatedly stated to be able to destroy Pandora and Pandora is implied to be largely composed of it's body. Was stated multiple time to literally eat stars and was consider a massive threat to the Eridians who could built moons, planets and even create vaults that houses a sun and numerous stars)
At least 5-C, possibly 4-C for Tyreen The Destroyer (Far stronger than her base form, consumed the Destroyer who (copy paste the Destroyer's 4-C reasoning here))
At least 5-C, possibly 4-C for Late-Game BL3 VHs (Stronger than their mid-game self. Defeated Tyreen the Destroyer)
Due note that the 5-C ratings comes from the moon feats and are a placeholder. They likely yield a higher result because Elpis is a fairly large moon. Same with the Destroyer shaking Pandora, which would be Low 6-B on an Earth sized planet but Pandora is huge.
Took my entire night trying to make this post but it feels worth it, let me know what you guys think.