There are many synonyms for the phrase "decisive arguments", which essentially means a set of compelling and convincing points or reasons that can help sway opinions or make a final decision. Some alternatives include "convincing evidence", "irrefutable logic", "persuasive rhetoric", "undeniable facts", "compelling reasons", "strong justification", "definitive proof", and "conclusive points". These words and phrases all indicate a level of clarity and authority in the argument being made, which is important in any debate or discussion where a decision needs to be made. Using these synonyms can help add variety to your vocabulary and emphasize the power of your argument.