The most common ending for a Disney villain is a fall. A long fall. And no wonder--it's dramatic and easy for the audience to not see the final splat. The places they fall from might change, but mountain or waterfall or clock tower, the end result is the same, as Ratigan shows.

Stabbing

Getting stabbed is a bit messier than falling. Plus, whereas a fall can be an accident or an Act of God, stabbing is directly caused by a hero, so there must be ample motivation to enable the good guy to come off well. Maleficent certainly got the point.

Death by Minion

A few unlucky souls are actually done in by their own henchmen and/or associates, such as poor Dr. Facilier. It might make a baddie think twice about how he treats those big stupid goons.

Death by Explosion

A loud and very theatrical way to go, with the added benefit that no body remains that can be potentially shown to viewers. It took a whole room full of fireworks to blow Shan-Yu to bits, but finish him they did.

Hoist on Your Own Petard

When the object you've coveted for the entire movie winds up killing you, a villain has to wonder if it is worth the trouble. Magic always comes with a price, as the Horned King now knows to his cost.

Shattered

An unlikely demise, unless, like Rourke, you are turned by a magically-infused shard of glass into a living crystal creature, and then fragmented into a million pieces by a loose propeller.

Hanged

By far the most gruesome ending of all is death by hanging, perpetrated by Clayton on himself, though quite accidentally. Brrrr!

Arrested

Some villains actually find themselves captured by film's end, destined to face society's justice. It would be interesting to see their respective trials someday. Alameda Slim is one example, but he may not find his ending so happy.

Trapped

Similar to Captured above, but without recourse to any law enforcement agency. These villains become prisoners due to the actions of the hero, though not in an actual jail. Hades falls into this category, even as he fell into the River Styx.

The final group is less a category than a catch-all for those who are left, alive, but defeated. Captain Hook swims for his life from the Crocodile, Cruella is last seen stranded by the side of the road, Madam Mim is sick but will recover, Shere Khan runs off into the jungle, Edgar finds himself on his way to Timbuktoo, Yzma is transformed into a kitty, and John Silver alone gets off scott-free, sailing away into the etherium.