Okay, I've made it pretty clear I'm entirely biased on the Antithesis.
X-666 is lame, annoying, and only surface level jabs that are boring and meaningless. Encephalon is just typical brains vs brawn type cliches. The Evangelist is pretty much what's expected for an alcoholic.
Ichor though... He's surprising. Not what you would expect completely for Ghost Rider. Fits on a surface level as much as the others. She's hellfire doing good and Ichor is Godlike liquid doing evil, but is it really that simple? The weapons don't seem to mesh either. Swords against chains? They don't seem as much opposites compared to the others, like pom poms vs knives, brains vs brawn, and a bible vs guns.
Let's start with the name Ichor. It's a two fold thing. Ichor is from greek mythology for blood of the gods. It's also an anagram for choir, the word used for a group of angels. This includes how they are specified. Angels fall into what's called The Nine Choirs. The Nine Choirs are Seraphim, Cherubim, Thrones, Dominions, Virtues, Powers, Archangels, and Angels. The hierarchy order tends to vary from religion to religion, but the choir names tend to stay. Cherubim, Archangels, and Angels are also part of the Heavenly Host, otherwise known as the army of God. Being of the heavenly host can also be a word play about being blood from that which hosts heaven/created and owns heaven. Which brings us back to blood of the gods. His appearance seems to play up both nods though the writing seems to solely be using his "Blood of the gods" nod so far. At this point though, only a third of the story has been released. His design and name overall show a rather deeper thought process involved compared to the rest.
So how does blood of the gods play into this? Well let's think about this for a second. What is it? Well in the greek references in specific it's a goopy like thick substance that's considered to be something only immortal gods could shed. It's also been used in relation to the blood of Christ which brings us back to the christian angelic references and heavenly host connection of Ichor's design. According to Lovecraftian lore, it acts and is described much akin to how the symbiote that comprises Venom acts. This includes how it seemingly abandoned the host it had when Ghost Rider defeated it. It left him in a crumpled heap as if Alejandra had broken the curse the mirror gave. Could it really be that simple and quick for a name derived from immortal beings?
What if it's not that simple? What if Ichor in particular was never the antithesis to Ghost Rider at all? There were 5 people that stared into that mirror if you think about it. Flash and the Symbiote could count as two. Plus with Ghost Rider being from hell and literally made of a hellfire demon, maybe she was immune to the mirror. What if Ichor is really the Antithesis to the Venom symbiote instead? The evangelist is pretty much directly tied to Flash Thompson, so the symbiote was seemingly skipped in this ordeal. Add in this is a plan from Blackheart, the son of the devil. A demon with ample arrogance that constantly causes him to make grand mistakes which backfire.
If this is the case, it makes Ichor the opposite to the symbiote. The weapon is blades/swords vs organic tendrils, a more natural opposite than metal hellfire chains. The venom symbiote being an alien that's evil incarnate now which feeds on negative emotions. Does this mean that Ichor may be more complicated hiding in a sea of characters that are only surface level cliches? It'd make for an interesting twist to say the least, would catch fans off guard, and would be something more up to what one would expect from Remender. He has a habit of hiding more complex ideas behind aspects that make you miss them at first until he's ready to use them. So is Ichor really the anti-symbiote that feeds off of positive emotions? A being who is 'good' but made to do evil right now like Venom is evil but being made to do good through Flash?
Personally I rather hope so. It'd yield an interesting twist. It'd create a new angelic like symbiote character to add to the Marvel stable of characters, and present interesting twists to what has been a rather bland story so far. It'd also put down some interesting groundwork for the upcoming Venom issues set to deal with hunting down Symbiotes. Besides of course Venom's own reaction to Toxin in earlier issues. Those are symbiotes of its own race though. Ichor would be something entirely new and without any complex alien race backstory to be concerned about anytime soon. Something that could be fun to play with and use within the confines of Marvel for all kinds of things in the future if they decided to dive into a 'divine' celestial symbiote angle much later. Then again, that's how Venom himself started too. Just a one off idea created from Secret Wars that grew into something much much bigger that quickly became a fan favorite.
Ichor represents a lot of possibilities and potential stories to tell using anyone from the Marvel universe. The parallels alone seem like too much to pass up, and I for one hope they use them to their advantage to give us something spectacular when we least expect it. Just imagine the sparring Ichor could have with the science created Anti-Venom. The self-proclaimed righteousness of a religious zealot against a being who literally is blood of the gods could make for some rather interesting stories and banter.
Of course, I could be entirely wrong in this too and Ichor could just be a simplistic idea of angelic liquid doing evil's bidding used against the Hellfire demon that punishes sinners. That's not as simple as I made it sound either. So let's hope if this is the case, they do go deeper into the complexity between these two. Zarathos, a demon who can be wielded by the host fighting Ichor, a liquid 'angelic' being that can't be controlled by his own wielder? Ichor of the heavenly host, a soldier made from the blood of gods against Zarathos, a hellfire bounty hunter/demon gone rogue? Liquid made metal holy swords against metal hellfire chains. Sounds good on paper, but just feels like it really lacks punch to it if that's the case. Still seems too simplistic and surface level reflection... (Which is entirely possible as intention due to how Thompson was in control at the time the reflections happened and it was just a mirror afterall. I might be looking too deep, but I expect deep from comic books.)