Power so great it develops personality

[u/icaromb25]

When a character has a power, but that power slowly snatches their body because it has a will of it's own.

Ex:

Jean Grey: Over many comics it has a deep connection with a primordial force in the universe which actually wants her to go out and create worlds through the universe.

Legion: The son of Charles Xavier who has way too many powers that start developing into personalities of their own.

Sentry: After being empowered all the darkest corners of his mind snatched his power creating the Void, an entity made of depression and hopelessness.

Hulk: After Bruce Banner absorbs a lot of gamma radiation he starts transforming into a being fueled purely by anger that doesn't share the other feelings with Dr.Banner, developing a personality of it's own with time.

[u/memisbemus42069]

[u/MostInteraction3184]

Kobik. Another Marvel example. A cosmic cube that gains sentience and has a really cute father/daughter relationship with Bucky.