Antonyms for the phrase "combined efforts" could vary depending on the context. However, some possible antonyms include individual efforts, uncoordinated actions, opposing strategies, and conflicting approaches. In situations where collaborating or working together is essential, the opposite of combined efforts could be divided efforts, solo approach, or disjointed actions. In a competitive context, the antonyms could be the single-handed endeavor, independent pursuit, or separate enterprise. Ultimately, the antonyms for combined efforts suggest a lack of cooperation, coordination, and unity. Instead, they imply fragmented, isolated, or divergent actions, leading to suboptimal results.