The phrase "most battle scarred" can be used to describe a person or object that has endured significant challenges and has the scars to prove it. Synonyms for this phrase might include "hardened," "weathered," "experienced," "resilient," "tough," or "battered." These words evoke the idea of having gone through adversity and emerged stronger on the other side. Another option might be "veteran," which implies a history of battles or challenges and a wealth of knowledge gained from them. Whatever word is chosen, it should convey a sense of hard-earned wisdom and strength.