Antonyms for the phrase "began where one left off" could include words like interrupted, ceased, discontinued, halted, and concluded. These words suggest a break or pause from a previous activity or task, rather than a seamless continuation. Other antonyms might be words like started fresh, began anew, or began from scratch, which connote a clean slate and a departure from previous work. Antonyms can help us better understand the nuances of a word or phrase, and provide alternative ways to express similar ideas. By exploring antonyms, we can build a richer, more precise vocabulary.