Metal Knuckles

Metal Knuckles, unlike his biological counterpart, is cold, he is a methodical version of the living Knuckles, he completely obeys the orders of Doctor Eggman.
He also has the ability to fly longer than the living Knuckles, and the Metal Copy is immune to damage.

Metal Knuckles is a robot created by Professor Dr. Ivo Rabotnik (alias Dr. Eggman). Metal Knuckles was created to fulfill Dr. Robotnik's desire to defeat Team Sonic: the team's leader, the incredibly fast Blue Hedgehog; the team's "brain," a yellow fox who flies on his two tails and is Sonic's best friend, Miles Prower (nicknamed Tails); and Metal Knuckles' prototype, a stubborn, serious, and very persistent figure who often gets angry. His main mission is to guard a very powerful and large stone, the Master Emerald (which has great strength), Knuckles the Echidna.
Metal Knuckles himself is an ally of Metal Sonic (Sonic the Hedgehog's prototype). He tries to emulate his prototype in everything. He shares Knuckles's characteristics. He is on the side of evil, and, along with Metal Sonic, is very loyal to his creator, Doctor Robotnik.
Metal Knuckles differs in appearance from his biological counterpart: he has spikes on his hands, reminiscent of Knuckles's boxing gloves, which have sharp metal spikes. Metal Knuckles also has a metallic shell, green sensory eyes, and boots similar to Knuckles', but metal, attached to his feet.