Durga Devi is said to be infinitely fierce to enemies and infinitely loving to her devotees. The following is a powerful sloka of Durga Devi that can be used by devotees to get rid of diseases and suffering.
Om namo devi devi durga devi sarvavyadhi vinashaya namosthuthe
ॐ नमो देवी देवी दुर्गा देवी सर्वव्यादी विनाशाय नमोस्तुते
Chant this sloka 12 times in the morning for 21 consecutive days, while holding a pinch of turmeric powder in your right hand. Eat the turmeric powder after the recital.