fitz is many things in my mind. he was good in the first several books, and his actions in exile are justified, hence the fact that he just lost his dad.
but then i started seriously disliking him once he got all freaked out about Alvar and Sophie's unmatchable status. i really think that maybe it was because of all the fitz hate i was surrounded with. there's a lot of people who dislike fitz, then decide to push their opinions onto new readers and then they start to dislike him, and so the vicious cycle continues.
then i realized, fitz is really not a bad character. in exile, he got really mad at Sophie and called her damaged. that was pretty mean, but that's just fitz's way of handling grief. grady and edaline shut themselves out, along with biana, keefe tries to find answers, and fitz is angry. that;s just his way of handling it.
yes, fitz's anger at everyone when the whole alvar thing was pretty bad, but justified. he has looked up to alvar his whole life. and to know that he's been secretly working with an evil organization that is working to hurt the people he loves, well that's awful and crazy and it means he's bound to make a few rash descisions. the reason he was so frustrated and kind of mean to everyone was because he felt like it was his fault. he felt guilty when alvar turned out to be evil, so he felt the need to catch him and stop him from hurting anyone else.
but his being an awful boyfriend about sophie's unmatchable status was defenitely the worst, yet i understand why he did it. the vackers had been through a lot ever since sophie came to the lost cities, and he was under a lot of stress to prove that the vacker legacy (the good one) was still a thing. he loved sophie, but once he learned that she was unmatchable, that means he would have to be a bad match if he got married her. as he and biana were already the first vackers to go to exillium, and they were accused (not directly) of ruining the good vacker legacy, so if he married her, he would also be the first vacker to be a bad match. but that doesn't justify his really bad boyfriend actions.
thank you for reading my very long fitz rant.
also remember this is just my opinion, so please don't be offended if i have a different opinion than you