The phrase "joined forces" implies cooperation and collaboration, suggesting a collective effort towards a common goal. Antonyms for this phrase could include terms that denote the opposite, such as "divided efforts" or "separate operations." These suggest a lack of unity, where each individual or group is pursuing their own interests, without considering the overall objectives. Other antonyms may include "conflicting agendas," "individual pursuits," or "competing factions." All of these terms suggest a sense of discord and fragmentation, where collaboration is lacking and cooperation is difficult to achieve. In contrast, the phrase "joined forces" celebrates the power and potential of collective action, where working together can achieve remarkable results.