Probably a 4/5! I've seen vaguely similar designs floating around - I think it's mostly the somewhat skull-like face giving that impression - but the specific details (as well as their yandere personality/story) makes him pretty unique in my opinion! Amadeus is a neat OC :)
edit: sniped, here's Vonny:
honestly? 4.5/5. I've seen a few scientist/villain OCs in my time, but I can safely say that this is the first one I've read about that gave themselves tentacles as a way to replace lost limbs. Giving themselves tentacles just to see if they could, usually as extra limbs? Sure! But like this? No! I mean, I rarely even see OCs with tentacle arms at all. I'm obsessed. I love him.