Question

Why does the electron transport chain produce the most ATP?

Answer 1

Cytochrome C Oxidase which is also called as Complex $IV$ of mitochondrial chain (respiratory) plays a crucial role in energy production in Aerobic respiration. It is the last step in the electron transport chain that is ETS. ETS's major role is to transfer electrons from carbon to oxygen/ $c$ to ${O_2}$ form $H2O$.

Complete answer-
Electron transport chain is an important participant in life supporting the organelle in function of ATP synthesis. Cytochrome C Oxidase is basically adhered to thirteen subunits. From which $3$ are copper ions, zinc and magnesium.
Cytochrome C Oxidase is the final step in the Electron transport chain and considered to be termination in the inner mitochondrial membrane, where it reduces oxygen (molecular) to free water, which allows ATP production. Meanwhile, copper chaperons are needed for assembling the Cytochrome C Oxidase complex.
Let us know about Cytochrome C Oxidase in detail- Cytochrome C Oxidase is a membrane protein large in structure and is encoded by mitochondrial genome. Cytochrome C Oxidase is blocked by the activity of cyanide which results in the blockage of ATP synthesis in the mitochondrial matrix. The leftover oxygen (${O_2}$) is consumed by cellular membranes and mediated by cyanide-insensitive quinol also known as alternative oxidase.

NOTE:
The Cytochrome c Oxidase other than being present in the mitochondrial matrix is also found in bacteria and archaea. There are defects involved in genetic mutations which alter the $COX$ complex which affect the ATP synthesis. Such disorders are detected in early childhood with high energy demands. Such as in organs- heart, muscle and brain. A dysfunctional cytochrome C oxidase is severe if altered.