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Debra (his adoptive sister) hates him, and says she should have killed him instead of LaGuerta (who found out about Dexter's secret). Her life's a wreck, and according to the preview for the next episode, she'll probably confess to the crime. Dexter doesn't love her that way, and she hates him, so all that's over now (much to the relief of fans everywhere).
I never made that big of a deal out of it, because I just never really cared. Sure I thought it was jumping the shark, but the bleak ending in season 7 and the great intro to season 8 more than made up for it.