Do you mean Lights and Thunder by Lyod? It's in one of the Demon Map packs
Geometry Dash Discussion

I do myself a favour and just stay away from the Demon Map packs since I know I'm nowhere near ready...

Wow! Not bad improvement considering I just posted 1098 stars only 3 days ago.
(Sorry the screenshot isn't loading some reason but I'm now at 1209 stars)

Funny, A_R, I played a bit this weekend and checked, I only have 1033 stars, which is less than you, LOL!
The fourth Demon Pack, "Demon Pack 3", is actually extremely easy. It contains The Lightning Road and The Nightmare, widely considered the two easiest Demon levels in existence. The other level, Crescendo, is not too hard with a bit of practice.
I also have 1/3 on a couple Demon Packs, notably Remix Pack 4 (beat xStep v2 this weekend, YEAAAAHHH), Demon Pack 1 (yStep by Darnoc was easy once I got the practice and timings down), Demon Pack 7 (Impulse is also one of the easiest Demons, it was my fifth after Lighting Road and Nightmare along with 2 other secret way/nerfed demons which have unfortunately been removed), and whichever Demon Map Pack contains Ice Cave by Ketis. Ice Cave is another level which really only requires timing and practice, and probably shouldn't even be a Demon in my opinion.
I also beat Invisible Clubstep (which I should have done when I beat Clubstep 20 months ago, FINALLY) the day after I beat xStep v2, which were I completed as my 12th and 11th Demon on Sunday and Saturday respectively.
I'm planning on taking on the following 4 Demons next: Deadlocked, Theory of Everything v2, Lights and Thunder, and Electroman Adventures v2, not necessarily in that order. My progress on those levels are 79%, 45%, 58%, and 46% respectively.
Bottom of the 1st page found... where? Sorry.