Close, end, conclude, finish, complete, terminate are comparable as transitive verbs meaning to bring something to a stopping point or to its limit, or, with the exception of complete, as intransitive verbs meaning to come to that point.
Close usually has latent in it the idea of action upon something which may be regarded as in some sense open as well as unfinished (see CLOSE vb 1).
End conveys a stronger sense of finality; it frequently has implicit reference to a progress or development which is thought of as having been carried through.
Conclude is a more formal term and applies particularly to transactions, proceedings, or writings that have a formal or special close.
Finish implies that what one set out to do is done; often, therefore, it connotes the completion of the final act in a process of elaboration (as polishing or perfecting).
Complete implies the removal of all deficiencies or a finishing of all that has been attempted.
Terminate implies the setting of a limit in time or space.