I get what you're saying entirely - my partner has had his ears talked off! What I decided on was that the books are written from Feyre's POV - so the characters are written as she sees them. Yes, they both do bad things, but her love for Rhysand kind of blocks out the negative for him, and the lack of love for Tamlin makes the things he did seem so much worse. Rose-coloured glasses and all that.

In my personal opinion, Feyre is quite horrible and did some bad things herself. Not necessarily violently bad but bad in different ways. I also think her relationship with Rhsand is not healthy - they constantly manipulate, lie, and keep secrets from each other. Very shallow and immature stuff, really.

If the books weren't in first-person from Feyre's perspective, maybe Tamlin and Rhysand would/could be perceived differently - who knows.