I would like to suggest the following for scaling.
Definitively scale: Moon Lord/Cthulhu/Your World*/The Terrarian/Celestial Pillars*
*Your World: Given that it is implied that the reason the dryad race was able to fight cthulu was their connection to the planet. They are also likely either the physical embodiment of the universe's or your world's will assuming they share an origin with the current dryad.
*Celestial Pillars: The Terrarian can only really upgrade from post golem gear by killing one and the monsters they summon and that is only offensively until after moon lord.
Should probably scale: The Torch god and Empress of Light*
*The Torch god and Empress of light: the terms deity, god, goddess, gods and others are used rather sparingly in terraria. Uses include the godly modifier and the golfer referring to your skill if you get 2000 or more points. In the lore however it shows up when mentioning that gods created the worlds, thd torch god and empress of light are a god and goddess respectively and in the Moon Lord's bestiary "Practically a god, his power knows no limits." This suggests his power is either equal to the gods or nearly equal and that gods are of a similar degree of power. The Torch God was willing to give their blessing to the terrarian for surviving the onslaught so they could be holding back. Empress of Light is absurdly power in daylight and honestly despite being post plantra is usually fought with post golem gear.
Likely scale: Terra blade*, Duke Fishron*, Martians*, Betsy*, Lunatic Cultist*, Frost and Pumpkin Moon bosses*
Terra Blade: The primary reason everyone else in this category is here and yes we have a profile for it. The weapon is post plantra, one of the best weapons in the game, and likely to help all the way past moon lord.
Duke Fishron: The only boss not directly referred to as a god or god like to have a five star rating in the bestiary. There is also the fact he is generally considered a post golem boss despite technically being available at the beginning of hardmode.
Lunatic cultist: I think he scales to a near pillar level terrarian, but you don't get to argue he scales to the weapons made from pillars.
Martians and Betsy: Post golem and terra blade.
Frost and pumpkin moon bosses: generally it seems these events are considered a post golem level challenge despite being possible pre-golem and the only attack any of the bosses have that does less than then golem's strongest attack is the contact damage of pumpking's main body.
Possibly scale: Golem* and Plantra*
Golem: You can get the terra blade pre golem however it creates the problem of melee armor being the same as plantra. Also it is the boss inside the area you get the item to summon the event that lets you get the last ingredient for the terra blade (Solar tablets for solar eclipses to get the broken hero's sword), and is in the same underground biome were you fight plantra. Lastly the lore of the martians invading from the Martian Probe, "Sensing growing power on the planet, otherworldly beings send space-age technology to scan for advanced lifeforms." The probes only show up after beating golem and only react to the Terrarian so it probably isn't the ritual the cult is doing but a power jump after beating golem.
Plantra: If golem gets to scale then we must acknowledge the fact between fighting plantra and golem there is no way to get better armor if terrarian is using a melee class and has the same defensive capabilities for both fights.
Technically scale: The weird category of enemies were they can under certain circumstances one shot a peak terrarian. This consists of an enraged skeletron, enraged skeletron prime, dungeon guardian, and wall of flesh
Skulls: All three one shot a peak terrarian outside unless they use a niche setup and only take chip damage from their attacks.
Wall of Flesh: this one is technically not an attack that does damage but if it reaches the end of hell the players will be licked and die which I don't think suggests death manipulation. I guess it scales by eating the players or maybe the tounge ignores durability since it acts as a damaging status effect.
Should probably not scale even with potential arguments: Any Hallow (Except EoL), Crimson, or Corruption stuff*, Eye of Cthulhu*, Skeletron (not enraged), The mechanical bosses (except enraged skeletron prime), Wall of Flesh (Outside of eating you)*
Hallow, Crimson, and corruption: Yes Corruption, Crimson, and hallow are meant to serve as the world's means of enforcing the balance they are implied to be similar across worlds, use methods besides physical force, and your world has unprecedented potential and none of these were of any help dealing with Cthulhu.
Eye of Cthulhu and Skeletron: Why would cthulhu's eye or skull have become infinitely weaker than when still part of him, they were presumably not supposed to have been separated for starts, much less how long it been.
Mechanical bosses: yes they we meant to replace body parts of moon lord, but they are not proven to be up for such a task.
Wall of Flesh: The World's core and master as it's guardian, it however doesn't have proof of scaling to your world.