I don't know about these two as I haven't watched either show, but from all the spoilers I would say U.S. Agent. Don't know about Sam or Wanda.

@PoolDeadpool2 John Walker doesn't count. We're talking about Sam & Wanda, no other characters.

I’d say Wanda she got her somewhat comic accurate suit, new revamped powers, and some character development

I think Wanda changed the most, not as a person, but she had a big emotional evolution...

Emotionally, Sam

After their first episodes I didn't care for either show so I didn't watch them and don't think I ever will.

^ Why?

Sam stayed strong with his convictions for the most part but found some acceptance for the symbol in the end. Wanda went thru a much mroe dramatic character change by letting go of Vision and her self interests.

Late to this, but I'm definitely going to say Wanda.