Who to give Bold Fighter to?

I got a +Attack -def Winter Ephraim which seems really mediocre. I kinda want to give Bold Fighter to someone that doesn’t have it yet and these are my options:
-Winter Fae (-hp +attack good for arena)
-Winter Cecilia
-Black Knight (Merged +1)
-Arden
-Halloween Dorcas
-Grima (+hp -speed) (Merged +1)

Should I kill him to give it to someone or keep him? If so who should I give to and how should I build them? Thanks in advance.