https://sufanon.wikia.com/wiki/White_Diamond_Killing_Juice The White Diamond Killing Juice is the only weapon known to harm and defeat White Diamond.
It was first used in episode 28 of season 5 as seen via this leak, https://www.youtube.com/watch?v=dQw4w9WgXcQ
It seems to be made of an opaque white liquid that steven couldn't get off his hand as it was too sticky.
The White Diamond Killing Juice was created by Greg "Stevens Fat Fuck Of A Dad" Universe, It was first used on Pink Diamond to create steven but it backfired and melted Pink Diamond as seen in episode 29 of season 5.
In the Samurai Jack and Gravity Falls cross-over episode (Which the Game Theorists noted is canon) Samurai jack notes how The White Diamond Killing Juice made him feel very uneasy and he nearly vomited.