Some people comment, and then there’s Xavier—the internet’s greatest reply guy. No one knows exactly who he is, but his knack for delivering razor-sharp comebacks has made him an online legend.

Victor Wembanyama had time, apparently nearly four years of it, to listen and reply to anything that internet trolls have to say about him. Wembanyama, the 2023-24 NBA Rookie of the Year award winner, ...