These are pretty cool Angel. The one on the right, I believe it's the Death Egg Robot mk.I, as seen from "Sonic the Hedgehog 2", along with the 3D rendered version from "Sonic Generations", and a mk.II(?) seen early in the game "Sonic Mania". As for the Death Egg Robot mk.III(mass produced), it's a very intimidating robot, though unfortunately... it's not as resilient as it's advertising to be. If anything, I'd choose the former over the latter due to it's more durable construct. As for the latter, it doesn't seem to take much damage, as it is demonstrated just before the Metal Sonic fight that comes shortly after.

I'm pretty sure the name of the stage where Sonic the Hedgehog and the player's OC character(whichever species he/she chose) blasts through the head of the robotic menace is called "Red Gate Bridge".

my theory on why the mass produced death egg robots are so easy to take out is that they weren't actually built, but rather are manifestations of the Phantom Ruby's power, like most of the rest of Eggman's forces. While tough enough to dominate a conventional battle field they're significantly weaker and less durable than a properly made one.

An interesting theory, don't mind me saying but... it's awfully difficult to prove such a theory since we only see the death animation for a brief moment, which makes it practically impossible to debunk.

I do have a very intriguing theory to share with you Angel. But, it involves a certain jackal A.K.A. Infinite (but it's based more around his origin story.) Care to hear about it?

sure, engagement is always fun

Okay, it may sound very farfetched but... what if Infinite isn't originally from the Sonic Universe? But, from an alterate universe entirely. To cut to the chase, Infinite is... Ardyn Lucis Caelum. The main antagonist from Final Fantasy XV. Like I said, it sounds very outlandish, but hear me out. What if Noctis didn't fully eliminate Ardyn from his universe, and somehow, someway, managed to get his soul trapped within the Phantom Ruby. I know, there are a few possible connections between the two individuals. 1) The two don't introduce themselves when the player eg; Noctis/Sonic first encounters either of them. 2) When they finally decide to introduce themselves, they only give out an alias, Ardyn Izuani for Ardyn and Infinite introduces himself by saying "You may call me, Infinite." 3) Both characters utilize red colored powers, red Miasma (the strange particle effect which is caused by the Starscourge) whenever Ardyn warps or attacks, while Infinite uses red colored cubes and dashes with a red colored aura. And that is only the tip of the iceberg.

I'll have to take your word for it because I have no idea who Ardyn is, I never played a Final Fantasy game

Ohh. My apologies. Feel free to check him out whenever you please Angel. There are others who might be intrigued in this.