I used a revenge spell

You cannot kill somebody with magick. It works within the laws of nature not like what you see in movies or in t.v. Hollywood makes it fantastical to make money. I dont think you need to get your head filled with ideas like that. It will make you crazy. If you feel guilty about the spell and dont want his spirit to be tormented because of you then do a cut the cord spell so he is no longer bound to you.

This post has some time to it, but after reading the responses I felt compelled to point out something. "Coincidental"? Really, now the individual did not say he attempted to cast a fireball and the target spontaneously combusted. He/she indicated that they sent out negative energy with a purpose, and the flow appears it was influenced. Shame to any who study and promote but then attempt to hide behind coincidence.

If you were wronged by the target then a balance was expected. All that you would have done was to initiate the desired response. If you do feel bad or guilty over the results then you should not have cast. If not then rejoice, sounds to me as you were favored by natures flow.