It shouldn't be necessary to write "Peter Quill". Normally a last name is good enough but, since this is the answer for P, "Peter" should also be good enough.
Maybe come up with another answer for K? Captain Marvel was briefly with the Kree, but what she really was before she was Captain Marvel was a pilot.
"Peter" cannot just be accepted because Peter Parker is also a name of a character. The alter-ego of a character usually means their first and last name (Bruce Banner, Tony Stark, Steve Rogers, etc). I have a couple other ideas for a K so I will change that. Thanks for the feedback!
Maybe come up with another answer for K? Captain Marvel was briefly with the Kree, but what she really was before she was Captain Marvel was a pilot.