Most of them I have beat with my old TimeBow. Even 1 victory vs Dark Matter, and Obliterator, and like 30-40% victories vs Graviton. Some I had never win, I won using RoL Hope or CCYB. In fact, CCYB is very good vs Octane and Seism, while RoL Hope destroys Divine Glory. Most FG are defeatable by at least one deck with a good to superb win rate. This is the reason I wouldnt vote for Dark Matter, for example, when the oracle tells about him, I use an unupped Aether deck and usually I win.
The ones I really think are the hardest ones at all, and I suppose theres no simple victory against are:
1) Hermes - even when the Oracle warn me about him, I skip fighting him. Too powerful.
2) Rainbow - ridiculous amount of control, and ridiculous amount of draws. His weak point, I assume, is the lack of creatures diversity. An PA Gravity Shield and some shockwaves for Shriekers could work, but I wont for now spend money getting an upped deck to beat him.
3) Dream Catcher - hes evil. His PC control is strong, and he has a good amount of CC and even BHs that usually force you to a rage quit. If his hand is good, I think no deck has a chance.
For now, most voted are Hermes (65), Rainbow (57) and Dark Matter (41), followed by Graviton (22), Dream Catcher (16) and Obliterator (14). Some FG with 0 votes: Elidnis, Fire Queen, Gemini and Incarnate. I wonder why someone voted for Miracle, Neptune and Paradox, lol. Each of these has 1 vote.