The word "dueller" generally refers to someone who engages in a formal combat or fight, often with weapons. Synonyms for this word include "combatant," "fighter," "challenger," "competitor," and "contender." Other related words might include "warrior," "gladiator," "samurai," "martial artist," and "fencer". These synonyms all convey a sense of someone who is skilled in the art of combat and willing to engage in a physical challenge or competition. Depending on the context, some other synonyms that could be used for "dueller" might include "champion," "hero," or "tough guy".