Became experienced can have many antonyms depending on the context it is used. Some of the common antonyms for became experienced are inexperienced, unskilled, novice, amateur, incompetent, and untrained. For instance, if someone has just started working in a particular field, they might be termed as inexperienced whereas someone who has been working in that field for years will be termed as experienced. Similarly, if someone hasn't received any training in a particular skill or activity, they'll be termed as untrained. All these antonyms indicate a lack of experience, skills, or knowledge in a particular area, which is the opposite of becoming experienced.