I like "double-edged sword" but I will offer a couple more ideas.
bane a person or thing that causes misery or distress (esp in the phrase bane of one's life) (Collins)
affliction 2. something responsible for physical or mental suffering, such as a disease, grief, etc. (Collins)
Examples of use:
The scientist's brilliant mind turned out to be the bane of his existence.
The artist's extraordinary sensitivity to beauty was, paradoxically, also his affliction.
