I'd say Shan Yu, his death was over like that! BOOM! ;)

I think that Ursula's death was even faster

^agreed, PrueFever! The other two were just painful... I think... I'm not sure, but Shan Yu just exploded... He probably didn't feel anything for very long!

Obviously Maleficent.
She was stubbed with a sword.

I'd rather get stabbed than blown up, scary!

seriously, who voted the evil queen out? She was nearly stuck by lightning, fell down a high rock, was squashed by yet another rock and then eaten by vultures. And during all that she was looking like an old hag (which might be the worst part for her)

At least the sword is sharper than the harpoon that killed Ursula.

...

Explosion. His death couldn't have hurted that badly...

Like people have been saying, explosion. Even if he lived through it, he probably lost conciousness really quickly.

It's her own silliness. Why should she change herself to be a big dragon that Phillip can easily stab. Or Ursula. Her case is almost like Maleficent's.