This happened from a combo of Jace1’s first ability and Floodwaters, almost certainly related to the exploit mentioned in another bug thread.
Only in this case, instead of getting negative power, the creature seemed to get infinite power.
It was a simple sequence, I used jace’s first ability on a creature and got a cascade that same turn that filled and cast Floodwaters. The creature’s power changed from 0 to something in small green type, and the next turn it hit me and took me from full health to nothing in one shot.
Because the game is not structured that way. It’s built around actions that are tied to a cards ID. There is not code specific to each card
they just need to update the action this card is using with a new variable so they aren’t relying on simply subtracting INT_MAX from the creatures power on cast