Hayley Atwell. Cobie Smulders. Elizabeth Olsen. Zoe Saldana. Natalie Portman.
Forgot Natalie Portman was in the MCU, because the Thor movies might be the most forgettable movies ever made. She would be no. 1 for me then. But I think she said she's not doing anymore Thor movies so I don't know if she counts anymore.