Season 7 has the reputation of being one of the worst if not THE worst season of Supernatural. Although I've been watching Supernatural since 2008, I've never revisited season 7 after its initial run.
Ah, Dick Roman. Roman was the representative face of all leviathans; the big bad of Season 7, and frankly, kind of terrifying. He not only killed Bobby Singer, Sam and Dean's father figure, but he also tried to turn the entire world into a meat market for him and his cronies.
The phrase 'Against all odds' means despite very low probability; in a most unlikely way. Example of use: "She managed to win the trophy against all odds."
If you do or achieve something against (all) the odds/against all odds, you do or achieve it although there were a lot of problems and you were not likely to succeed: Against all the odds, he recovered.