The Darkness took over BFB..
When someone is corrupted, their eyes will go white and their pupils will be replaced with some particles of corruption, signaling their loss of control, their limbs will elongate, and will also have some patches of black pixelated liquid on their body.
A corrupted will lose their entire personality and will act like a dangerous, mindless, aggressive predator.
A corrupted will also act predatorily obsessive over their loved one and will actively target them.