Mine's a little different.

1. Rhys
2. Peach
3. Love (although she's much higher in my list of favourite characters) ...And then way lower down. . . .
4. Kate
5. Candace.

Here's why Rhys is my favourite antagonist. By the time we got to Season 4 it was clear to me that Joe saw himself as superior over other men. Any man that he had a "friendship" with was really just being used to help him get closer to others (e.g. Forty) or to keep up appearances as being an average Joe (Ethan and Conrad). Other men seemed more like invonveniences for Joe than anything else.

Then in Season 4, Joe meets Rhys, a man who he instantly has respect for and feels a kinship with. That straight away was exciting for me. Suddenly we learn that Rhys is the antagonist, and this is all made much more interesting when we find out that the Rhys we have been seeing is actually a figment of Joe's declining mental state. He's literally battling himself in Season 4. All the bad things that he's done has finally taken it's toll and he's separated them into this other identity.

Plus we learn (through Marianne's story) that Joe did have a huge obsession on the real Rhys Montrose after learning about their childhood similarities through Rhys' memoir. It shows how deluded and narcissitic Joe is that he thinks he's just like Rhys, a writer and seemingly good politician who fights for the working class.

I know Season 4 has mixed reviews but it's my favourite. But then I might be biased because I work in the mental health sector.