Hikaru accused Luis Paulo Supi of cheating at least twice.
From his Wikipedia article:
```
In an online blitz tournament hosted by the Internet Chess Club in May 2015, American Grandmaster Hikaru Nakamura accused Supi of cheating (Supi had defeated Nakamura).[2] The tournament judges accepted Nakamura's accusation, reverted the match's result, and banned Supi from the tournament. Brazilian Grandmaster Rafael Leitão wrote in his personal website, "Accusing him of using an engine in this match is absurd. The match is full of tactical mistakes. Nakamura played extremely poorly and, honestly, wouldn't have survived long against any engine given his terrible opening.".
```
Some years later Nakamura lost 4-0 and again insinuated that GM Supi used an engine.
Despite all that, Nakamura still published a video calling him a "legend" for once beating Magnus in 18 moves
From his Wikipedia article:
``` In an online blitz tournament hosted by the Internet Chess Club in May 2015, American Grandmaster Hikaru Nakamura accused Supi of cheating (Supi had defeated Nakamura).[2] The tournament judges accepted Nakamura's accusation, reverted the match's result, and banned Supi from the tournament. Brazilian Grandmaster Rafael Leitão wrote in his personal website, "Accusing him of using an engine in this match is absurd. The match is full of tactical mistakes. Nakamura played extremely poorly and, honestly, wouldn't have survived long against any engine given his terrible opening.". ```
Some years later Nakamura lost 4-0 and again insinuated that GM Supi used an engine.
Despite all that, Nakamura still published a video calling him a "legend" for once beating Magnus in 18 moves