Determining the "most popular" K-Pop idol can be subjective and may change over time due to evolving trends and fan preferences. However, as of my last update in September 2021, one of the most widely recognized and popular K-Pop idols is BTS, also known as the Bangtan Boys.
BTS, a seven-member boy group formed by Big Hit Entertainment, has achieved unprecedented global success. They have amassed a massive international fanbase, known as the "ARMY," and have broken numerous records in the music industry. BTS is renowned for their powerful performances, meaningful lyrics, and their ability to connect with fans on a personal level through their music and social media engagement.
The group's achievements include topping charts around the world, achieving multiple Billboard Hot 100 No. 1 hits, selling out stadium tours, and receiving accolades from various award ceremonies. Their impact on the global music scene and their ability to transcend language barriers have solidified their status as some of the most popular K-Pop idols worldwide.
However, please note that the popularity landscape in the K-Pop industry can change rapidly, and there are other incredibly popular groups and solo artists as well, such as BLACKPINK, EXO, TWICE, and more. It's recommended to check the latest sources or official charts for the most up-to-date information on K-Pop idols' popularity.