Yeah, so, for me it was the god of Mithala. That guy caused me SOO much pain... ugh. I probably would have said the sun temple worm, but a glitch allowed me to beat him pretty easily (I feel sorta bad, but not really

)
Even after I figured out how to kill him, it still took me about 20 tries. When I did finally manage it, I felt so satisfied; it was great.
The Jellyfish king also gave me some trouble.
What was your hardest boss? What about your favorite boss?