The ending was all Scowl's fault (Spoilers)

Snow White and the Dwarfelles end up defeating Maliss in the end when Thunderella distracts him momentarily and Snow White is able to grab the cloak from him and cover him with it long enough to turn him to stone.

HOWEVER!

None of that would have happened if the dwarfelles hadn't made it into the castle in the first place. It was Scowl that decided they needed to capture one of the dwarfelles and when they attempted to carry Sunburn into the castle she ended up being to heavy and they fell into the castle courtyard which allowed her to lower the draw bridge so the rest of the dwarfelles (as well as the Shadow Man/Prince-in-disguise) to enter the castle and fight Maliss.

If nobody had entered the castle to save Snow White or fight back against Maliss to save her, she most certainly would have been turned to stone.

So in the end, the biggest mistake Lord Maliss made was not making sure that Scowl was eliminated before he attempted to kill snow white.

I found this mildly hilarious