It depends of course on the nature of the healing magic and how fast it's working.

The three things I'd try:

• Can a spell used to staunch blood flow also be used on a non-bleeding target causing massive blood clots?

• Is there magic to increase Insulin production for diabetics? Will put victim in a coma and eventually kill them.

• Are there any spells to anesthetize the patient? Is it rapidly working? Can it be quickly and conveniently cast if I don't care whether the patient ever wakes up again?

If the magic "magically" only works on the intended wounds/diseases/maladies then it will be hard to use them offensively. However, if the magic works more or less like modern medicine there are a lot of creative uses that will ultimately kill the victim.

It depends of course on the nature of the healing magic and how fast it's working. I'll assume the magic is more or less equivalent to modern day medicine and that it can be used without the prerequisite of an existing condition to cure.

The three things I'd try:

• A spell used to staunch blood flow also be used on a non-bleeding target causing massive blood clots.

• Magic to increase Insulin production for diabetics. Will put victim in a coma and eventually kill them.

• Spells used to anesthetize. These are basically sleep spells designed so that the patient does not react to damage and wake up. They must work fairly quickly and once incapacitated the victim will be an easy target for any other attack, magic or otherwise.