Gil Fronsdal has a discussion on his website of ill will as one of the most common of the hindrances we can experience in meditation. He looks at some of the ways ill will expresses itself and discusses several ways of investigating it and relating to it. You can find his article here: The hindrance of Ill Will
Sharon Salzberg points out that fear and anger are both forms of aversion that differ mostly in their expression. She suggests that while we may never be completely free of fear or anger, we can change our relationship to them. You can find her article here: Fear and Anger are the Same Mind State
Vanessa Zuisei Goddard has a short article on ill will that includes several tips on working with it. You can find her article here: Working With the Five Hindrances: Ill Will