Dictionary

what has been seen cannot be unseen en · X

Repulsive, disturbing, or horrific sights can never be erased from memory once they have been seen.
- I went into Akira knowing it's considered amongst critics a landmark film for anime and the success of the genre in America, but I was also expecting the type of weirdness that has given anime an infamous reputation in pop culture. Don't know what I'm talking about? Google "hentai." …Actually, no, don't do that. Seriously. Don't fucking do that. What has been seen cannot be unseen. 2011 December, Jay Wallace, “Akira”, in BandWagon Magazine:
- At Dachau he was witness to real rather than abstract suffering; what has been seen cannot be unseen, nor can it be rationalized. 2010, Brad Prager, “Suffering and Sympathy in Volker Schlöndorff's Der neunte Tag and Dennis Gansel's NaPolA”, in Paul Cooke, Marc Silberman, editors, Screening War: Perspectives on German Suffering, Camden House, →ISBN, page 196:

Spelling	Features	Labels	Source
that which has been seen cannot be unseen		alternative	lexicographic