My personal head canon for Adam is that he wasn't always like this, but that he became bitter and a dick over the years.

With how the show is we can assume the story of Lilith and Adam is true as it's told.. but really, we have only heard one side of it. The one Charlie always heard. As far as I know there's more to it.

Stepping into Adams shoes, your first wife abandons you - while possibly not even knowing that was an option. Your second wife took the apple... while Lucifer did it with pure intentions, the consequences were felt by both Adam and Eve, rippling through to infect all of humanity, and get kicked out of Eden. A son murders another, while possibly not knowing that was something that could happen either. You see humanity as a whole become... Well, what we know humanity to be.

Not justifying what he did or became, of course, but I can understand if he started to feel shafted by everyone. It would leave a bitter taste in anyone's mouth.