A giant-killer is a person who achieves a remarkable feat by defeating someone or something bigger, stronger, or more powerful than themselves. There are several synonyms for the term "giant-killer" that can be used to express the same sentiment. Some of these synonyms include champion, conqueror, hero, victor, winner, slayer, destroyer, vanquisher, and overcomer. Each of these words highlights the courage, determination, and strength required to overcome seemingly insurmountable obstacles or challenges. Whether it's in sports, business, or personal life, being a giant-killer requires a combination of skills, perseverance, and grit to achieve success.