I have mixed feelings about him. He was treated beyond bad by just about everyone. Not to mention being resurrected without consent and abandoned by Victor.

I think I hated Frankenstein the most. Talk about whiny! Also he was arrogant, condescending, uncaring, selfish, spoiled and childish. On top of that, a disgusting junkie.

I think Lyle was one of, if not the most human character. He was kind and willing to sacrifice his reputation and even his life for his friends.

I agree with you on both instances. Frankenstein was very conceited, and given to making sarcastic and judgmental comments about the opinions others expressed. He expressed the kind of arrogance many scientists display. I have degrees in chemistry and pharmacy so I know about scientists. It disgusts me to see the arrogance which some colleagues display. It prevents them learning.
They have the attitude that "Science" has answered the essential questions, that as scientists they can judge authoritatively on unexplained phenomenon. "If I have not heard of it, then it must not be true" could summarize some of the arrogance they display. Certainly Victor acts this way when people suggest that vampires or witchcraft are real. Victor has no explanation, but since science does not explain or allow for anything supernatural, he simply scoffs at other explanations.

Lyle plays one of those characters who is hard not to like, even when he makes a mistake.

As far as John Claire, at times he is a sympathetic character. And you're right that many people recoil when they see his scarred face. But he is a violent, murderer, and he is not only mean to Victor. At times the slightest frustration elicits violent outbursts and actions by him toward strangers. I know the writers intend for the viewers to feel sympathy for Claire and to overlook his murderous actions. But would anyone just forgive him in real life? Many people in real life suffer rejection and other unfortunate emotional injuries, and most of them refrain from murder. It was good that he found his family again, regained his memories, and was able to care for them for a while. He seemed to have matured by then. But as I said, I never really got over his behavior in the first few episodes.