If "debutante" refers to a young woman making her social debut:
* Veteran: This implies someone with experience, the opposite of a newcomer.
* Experienced: This emphasizes having knowledge and skills acquired over time.
* Mature: This suggests someone who is no longer a young, inexperienced person.
* Established: This indicates someone who has already achieved a certain level of success or recognition.
If "debutante" refers to a first performance or appearance:
* Veteran: Again, this implies someone with experience, the opposite of a debuting performer.
* Seasoned: This suggests someone who has been performing for a significant period of time.
* Experienced: Similar to "veteran" and "seasoned."
* Established: This can be used for someone who has already gained a reputation in their field.
Ultimately, the best antonym for "debutante" will depend on the specific context of your sentence.