The Juggernaut: 10
J.T.: 10
Vez'nan: 10
Gul'Thak: 10
Sarelgaz: 10
Greenmuck: 10
The Kingpin: 10
Ulguk-Hai: 10
Moloch:10
Myconid:10
Lord Blackburn:11 (+1) - Both my favorite boss and a pretty difficult one.
Nazeru:10
Quincon:10
Umbra:10
Leviathan:8 (-2)
(+1) - Clearly the most intimidating boss - Leviathan is simply pitiful. He's slow, [i]stops himself[/s], and doesn't have any remarkable powers. His path is also long. And he's squishy.
Vasile:10
Xyzzy:10
Hi Hi Enha:10
Malicia:10
Spider Goddess:10
Bram:10
Baj'Nimen:10
Godieth:10
Bolgur:10
Jokull:10
Gerald Lighseeker:10
Paragons:10
Polyx the Wise: 10 - Polyx gets completely BODIED by Blazing Gems, but I'll save him for later since there are easier bosses.
Winter Queen:10