Alright, Eldritch!
Alright, first of: I have no problems with the size. I always viewed a Gorgon as being pretty big. Their upper torso would still be human sized (I'm talking about the typical Gorgon myth here, not a correction to your character) so having the Snake tail be as long as it is, is to be expected. He's a lumbering giant even as a human, so being the size he is when Shifted is alright.
Now... There's the matter of his powers. I feel like his Gaze is too powerful. He is, literally, a "Look into my eyes and-ohyou'redead" character. The
second he gets eye contact with you, you can't do anything to survive. I feel like it should be possible to break his gaze, but it would take a significant amount of willpower. You could keep the pain the gaze courses (if lower it a bit so as to not make it torture levels of pain) to even it up a little. Willpower is difficult to muster when you're in pain. Note that only humans (or really, really big animals) would be able to break from his gaze. A dog or a monkey, or even a small child would be helpless. In his Full Gorgon Shift, I feel like it goes from 9 to 11. Not only is it instant paralysis/freeze, but it's also torture-levels of pain that would knock out a grown man (You didn't describe it as such, but that's what it sounds like).
As for his venom, while I understand that it can be both deadly and should paralyze its victims, I feel like it's a bit too much that he an also breathe it. As if being a hulking behemoth that can barely be harmed by any physical attacks save blunt force wasn't enough, he can also blow at you like he would a candle and watch you die. And if you hold you breath, then he can just poke your arm with one of his teeth and watch you die as well. And even if
that doesn't work, then he'll crush you.
I get that he's large and has a ton of muscle (like any snake would), but he just has way too much in terms of raw power. As it is, if he wants to kill someone there's absolutely nothing they can do save gouge out his eyes before he even Shifts. There's no way to survive if he wants to kill you, as he just looks at you and you're doomed. You need to tune that down quite a bit before it's at a point where he can actually be fought. Every Shifter has strengths and weaknesses. Gregory has raw power and durability, but his attacks aren't the fastest in the world, and could be avoided if you're quick or smart enough. Lily is quick and difficult to hit, but she is still just a normal human when it comes to her physical attributes. She's trained and can run for a long time, but even then she has to rely on her magic to avoid taking any hits: She's fragile compared to the rest of you.
Liza has the range and is capable of moving in three dimensions, but she's somewhat fragile as well and isn't really the most combat focused from what I can see. And then there's your guy: Penetrative weapons are useless. Blunt weapons somewhat useful. Physically strong. Fairly quick even if fully Shifted. Instant paralysis gaze with incredible pain. Deadly venom with no cure (almost). Enough physical strength to crush a human's body... He just has no weaknesses. Yeah, Lily could run circles around him if he's fully shifted, but how much is that worth if he can just look at her and then it's over?
You need to tune it down to a level where he has some obvious weaknesses, or at least give whoever he's up against a fighting chance. Specifically, there should be a way to cure the venom that isn't just his blood or magic healing. Just one more way that there is access to, as well as make it possible to wound him. With how tough his scales are now he's more or less impervious to most physical attacks. Otherwise you could kill off any one of our characters if you so desire, and that's not the point of this.
You mention that he knows three languages, and while Japanese and English are sort of a given (grew up in Japan, and English is also used in Japan and in most of the rest of the world) I would also like to know how and where he was taught German. I don't think you wrote anything about it in the Background.
The last thing that I have a bit of a problem with is this part:
Hiring a number of shifters
Where exactly did he find those Shifters? Yeah, he might find one or two in the underground world, but there aren't very many, so finding a handful of them in just one city is incredibly difficult. Furthermore, people such as them would likely do everything they could to hide, and many were recruited into the Army. Either flesh it out and give us some more details as to how he found several other shifters (most of which would probably come from out of town, or even out of the country. Perhaps bribing the corrupt one(s) from the military?) or reduce it to one or two, please.
Aside from that, I think he's an interesting character. I'll admit, when I read it initially all I could think of was "Great... a guy who wants to rule all of us. Woo!" But then I read what his personality was and I kinda got to like him.