The slang term "offed" means to kill or murder someone, and as such, there aren't any true antonyms for it. However, if we look at the opposite meaning of the word, we can infer some appropriate antonyms. The opposite of killing someone would be to keep them alive, so some potential antonyms might be letting live, saving, sparing, or preserving. Additionally, we could use words that suggest preventing or avoiding harm to someone, such as protecting or guarding. While these words do not have the exact opposite meaning of "offed," they are likely to be used in the context of preventing death, which can be seen as an antonym of sorts.