Demonic Illusion: Hell Viewing Technique (Earth-2356)

This technique subjects targets to visions of their greatest fear, regardless of whether or not they're aware that they're afraid of it. This "fear" can be something that the target is actually scared of or merely the one image that they least want to see. When Obi-Wan Kenobi used this technique on Sakura Haruno, he made eye contact with her as he activated it. Obi-Wan then seemed to disappear in a swirl of tree leaves, leaving behind what Sakura feared: a dying Sasuke Uchiha. Being presented with such a gruesome image, one that, at the time, Sakura believed to be real, gave her enough of a shock that she fainted to see it.

Source

 * https://naruto.fandom.com/wiki/Demonic_Illusion:_Hell_Viewing_Technique