In Heroes what powers does Niki Sanders have?

Answer 1

Actually, Niki Sander's power is super strength and not alter ego. Her alter ego is due to her double life (mom by day, internet stripper by night) along with her suppressed anger on her life and craving for fun. which eventually cause her to have split personality mental disorder.

the alter ego of Jessica was created to give niki a sense of wild life and with the super strength, she was unstoppable.

but meanwhile, when in her own Niki state, her power is suppress as Niki is convinced that it was Jessica's power until Jessica convinced Niki that it is Niki's power when Niki was in trouble and Jessica was also surpress (is rather complicating. watch the show. but if you have to know, it had something to do with candice shape-shift into Niki and the real Niki thought it was Jessica who had break free again)

Jessica eventually was fully suppressed due to formation of Gina, another alter ego.