It's impossible to say who has definitively declared Rihanna the "best singer" as opinions on music are subjective and vary widely. While many people admire her vocal abilities and artistry, there's no single person or source that holds the authority to make such a statement.
There are countless music critics, fans, and industry professionals who have praised Rihanna's talent. However, their statements often focus on specific aspects of her artistry, such as her vocal range, stage presence, or influence on popular music. Ultimately, whether or not someone considers Rihanna the "best singer" is a matter of personal preference.
