The phrase "powerful demonstration" means showing or proving something in a strong, impactful, and convincing way. It can involve displaying evidence, skills, or emotions that strongly support or emphasize a point or idea. Full definition
To me the most powerful demonstration of Celestia's open - ended system is another Thorvaldsen creation. (discovermagazine.com)
Juicy Excerpt: The most powerful demonstration of the phenomenon is the famous research that was done by Solomon Asch in the 1950s. (arichlife.passionsaving.com)
This month South Africa has seen powerful demonstrations around labour rights in mining, with 34 protestors shot by police. (blog.politics.ox.ac.uk)