Who is the scariest hackers?

Could you please elaborate on who you consider to be the scariest hackers in the world today? Are they individuals, groups, or perhaps even nation-states? What sets them apart from other hackers, and what sort of damage have they been able to inflict on systems and networks? Are there any specific cases or incidents that have left a lasting impression on the cybersecurity community, showcasing their prowess and making them stand out as particularly formidable adversaries?