Black spells and curses are pretty popular topics around here, though the dark magick aspect of curses aren't for everyone. Actually, the tern "curse" is a little vague, and isn't all that different from the usual black spells.
Curses are usually intended to cause someone bad luck or direct harm, I suppose. Anyway, here is another page of powerful spells you can use when you need to make a impact on a situation with a little black magick.
The Garlic Bane
This spell is to capture someone's energy and put their life on hold. It doesn't really cause any harm, but they won't be able to really get anything accomplished until it's broken or you end the curse. You will need to have:
Choose your jars so that the little one will fit entirely inside the big one, including when lids are on. A pickle jar and a small jam jar would work fine, for example.
Use a heavy black marker (no pencil or ball point), to draw a pentacle on a piece of paper, then cut it out to fit inside the bottom of the big jar. Place the garlic cloves inside the smaller jar, and tighten the lid. Repeat the first words of the spell:
Moon will wax, moon will wane,
Now I cast the garlic bane.
Set the little jar inside the big one, on the piece of paper. Now mix ash and dirt in water, and pour into the big jar enough to cover the smaller jar. Doesn't have to be completely full, just enough to cover the jar with the garlic. Say:
My power and my might,
I bring it out this night.
I trap you in this jar
Now your luck is far
Suffer in an empty space
Living at a slow snail's pace
Nothing works, nothing gains
I cast on you, lots of pain
As the ink washes off the paper into the water, the spell will gain energy and start to work in a few days. Leave the entire thing on your altar for it to keep working. Repeat the words again over the jars to recharge the spell after a month, if necessary.
Black Cat Bone
This spell and curse is a variation on a classic hoodoo spell, but with a twist. You don't need a bone from a black cat either. This ritual is a simple bit of black magick to bring harm or general bad luck to your victim.
On the night of the dark moon, paint the bone completely black (don't miss any bits). Let it dry, and then use the silver needle to scratch 5 small x's in the paint. You might want to get a bone big enough to allow this or it can be frustrating.
Now, you have to put the bone somewhere that the person you are targeting will find it and pick it up. You can't just hand it to them either. They have to find it on their own. It doesn't matter what they think or if they throw it away after. As long as they touch it once, the curse will begin.
Don't take these black spells and curses lightly. They can be powerful magick and may have more effect than you expect.