Bioshock Infinite's ending is a paradox (therefore huge plot hole)
Going back time killing DeWitt/Comstock does only one thing: to create a new universe where DeWitt/Comstock died during baptism. The DeWitts and Comstocks still live in their original universes. In multiverse time travel, intervention by going backwards only creates new universes, It CANNOT alter the universe the time traveller comes from. This is the only way in which backwards suicide is non-paradoxical.
DeWitt killed -> No Comstock -> No time-dimesion traveling Elizabeth -> No one kills DeWitt
You CANNOT have both multiple AND disappearing Elizabeths (as in the drowning scene). If it's a single-verse, there wouldn't have been multiple Elizabeths. But then if DeWitt is killed, there wouldn't one Elizabeth at all. If it's a multi-verse, there wouldn't have been disappearing Elizabeths. Because doing so only creates a new reality where there is no DeWitt/Comstock, thus no Elizabeth. But Elizabeths in the original realities still exist, possessing time and inter-dimensional travelling ability. Being both single-verse and multi-verse is a paradox.
Going back time killing DeWitt/Comstock does only one thing: to create a new universe where DeWitt/Comstock died during baptism. The DeWitts and Comstocks still live in their original universes. In multiverse time travel, intervention by going backwards only creates new universes, It CANNOT alter the universe the time traveller comes from. This is the only way in which backwards suicide is non-paradoxical.
DeWitt killed -> No Comstock -> No time-dimesion traveling Elizabeth -> No one kills DeWitt
You CANNOT have both multiple AND disappearing Elizabeths (as in the drowning scene). If it's a single-verse, there wouldn't have been multiple Elizabeths. But then if DeWitt is killed, there wouldn't one Elizabeth at all. If it's a multi-verse, there wouldn't have been disappearing Elizabeths. Because doing so only creates a new reality where there is no DeWitt/Comstock, thus no Elizabeth. But Elizabeths in the original realities still exist, possessing time and inter-dimensional travelling ability. Being both single-verse and multi-verse is a paradox.