My problem with Bethany is that she doesn’t have a lot of personality. She just sort of goes along with what you do. I guess she sort of implies she’s bi at some points in the game but that’s pretty much everyone except Carver, Varric and Sebastian (Remember Carver likes Merrill).
I like Carver because he actually has an interesting story dynamic. No matter what you do he is trying to prove himself and soldier on. Even then he expresses a lot of loyalty even if he hates you. To me this makes him the best character in the series because to a guy like me he is relatable. I have family I don’t like but I stand by them when needed.
Alternatively you get him to like you. And you are sort of a hero to him by that point. Since I am religious and I play a mage in that game I usually let Carver become a Templar - because it does make the game more interesting and gives his character a different layer of depth what with his interest in Merrill and I play a female Hawke so his sister being a Mage. Even as a Templar he stands by you.
Alternatively if he becomes a Warden he actually does thank you for saving him a few times if you and him aren’t rivals. It’s sort of heartwarming. But I see the canon end as him being a Templar and kind of just pissed off you never took him to where he gets Darkspawn AIDS and has to join the fantasy French Empire for the rest of his life fighting weird mutants for 10-15 years. Being a recovering alcoholic that goes to Church all the time and maybe getting with a Welsh chick with face tattoos and pointy ears sounds like a better life. Also gets him some powers if you play Legacy.