SPOILERS
I swear, I got lucky on time attack and found a shortcut at the first blast gates. After that, the only advice I can offer is to position yourself just barely touching the symbol on his head. He won't be able to shake you that way.
END SPOILERS
I guess I'll throw my lot in and declare the hardest boss I ever dealt with to be Robotnik from Sonic 2 & Knuckles. Now I know I can simply hit him when he plops down on the ground, but I've only ever done the fight when I was younger, and I was damned impatient after spending the (usually) afternoon on the game; so I'd get to him and take every risk I could to get just one more hit in.
Then it would happen. Knuckles would float through Robotnik and die. I can recall beating him once or twice, but it was so enraging that I almost never play Sonic 2 with Knuckles.