Man, what kind of horror are you into that none of this stuff bothers you?!?
I THOUGHT THIS WAS A SAFE SPACE
Kidding aside... there's definitely a horror element to G1 Unicron but outside of that opening scene it's really not what I'd call "cosmic" or "Lovecraftian."
There are scary elements sure, but Unicron ultimately ends up as an obstacle who wants the MacGuffin.
Armada Unicron, by contrast, is presented in this eerie sort of way. He has a "herald" who comes off as possessed or otherwise mad and yet also duplicitous. He's controlling a salt plant with unnatural looking metal plant life and a
flesh metal puppet doppelgänger of the main hero. He's only ever hinted at or shown in shadows in dark visions at first.
When he finally makes his move the mood over Cybertron is almost eerie and disconcerting at first. He drives Thrust mad while ultimately not even caring about him or realizing he's there. His insides, like '86, have a very non-Euclidean feel to them, but whereas '86's time spent inside was the climax of an action adventure, Armada spends a lot of time with the characters trapped in this eerie space just trying to figure things out. Rad has dark prophetic dreams.
And while we eventually do get our action adventure climax (Armada has the best Optimus/
Megatron Galvatron fight and I will stand by that) even this has a cosmic horror tinge to it with Unicron revealing his motives... he's not after the Matrix, he doesn't want to conquer the universe, he just feeds on fear and hatred and has been fuelling Cybertronians' worst instincts to goad on a destructive war to feed that hunger.
'86 Unicron is great, but Armada Unicron leaned as far into the idea of Unicron being this Lovecraftian elder god as a kids show reasonably could, and I love it.