The antonyms for the phrase "blunders up on" would be words or phrases that convey accuracy, precision, and calculated actions. These antonyms could be terms such as "executes flawlessly," "handles with skill," "manages expertly," "accomplishes with finesse," or "navigates adeptly." By using these antonyms, one can communicate the opposite of making mistakes or errors while carrying out a task or action. These words and phrases convey a sense of competency and mastery, unlike the phrase "blunders up on," which denotes a lack of control and often implies mistakes or failure.