Yes, all three spellings, "anti-hero," "antihero," and "anti hero," are commonly used and can be considered correct. When it comes to compound words, such as "antihero," it is common for different sources to use different spellings or hyphenation styles. In this case, both "antihero" and "anti-hero" are widely accepted and convey the same meaning. Similarly, "anti hero" without a hyphen is also used, though less frequently. It's important to note that while all three spellings are technically correct, consistency should be maintained within a single piece of writing.
