The phrase "final battles" can be replaced by various synonyms depending on the context. For example, "last confrontations" can be used to describe the concluding fights of a conflict. "Ultimate clashes" can also be used to denote the last intense battles. Another synonym for "final battles" is "decisive struggles" which emphasizes the critical nature of the fights. "Final showdowns" and "endgame battles" can also be used to describe the final battles of a war. In any case, the use of synonyms helps to spice up your writing and eliminate redundancy.