Is KGB powerful?

Could you elaborate on the supposed strength of the KGB? I'm curious about its historical significance and whether it was truly a formidable intelligence agency during its heyday. What were some of its most notable achievements or operations? Additionally, how did it compare to other intelligence organizations around the world at that time? Was its power mainly derived from its sophisticated technology or its extensive network of informants? Or was it something else entirely? I'm interested in understanding the full scope of the KGB's influence and whether it truly deserves its reputation as a powerful organization.