Found 3 cards from my collection that only list the front side of the card instead of both the front and back with the "//" between the card names:
Ulvenwald Captive // Ulvenwald Abomination Eldritch Moon 175
Delver of Secrets // Insectile Aberration Innistrad: Midnight Hunt 47
Liliana, Heretical Healer // Liliana, Defiant Necromancer Commander Collection: Black 1