What does it mean if you dream about someone you used to like but now hate committing suicide?

This suggests some guilt feelings on the part of the dreamer. While it is normal for friends (or couples) sometimes to drift apart, swinging to the extreme of hate tends to cause confusion, particularly on the level of the subconscious emotions. The "suicide" indicates a sense that the dreamer's hatred is hurting the former friend. The dream reveals nothing about the former friend's actual thoughts or feelings.