The word "killer" can have various synonyms depending on the context. For instance, if we're looking for synonyms in the context of a murderer, we can use words like assassin, slayer, or homicidal maniac. If we're talking about something deadly, we have words such as lethal, poisonous, or fatal. In the context of something impressive, we can use words like amazing or incredible. Additionally, words like strong, powerful, or forceful can be used to describe something or someone that's capable of causing significant harm. Overall, there's a vast range of different synonyms for the word "killer," and choosing the right one depends on the situation and context.