I was adopted (full adoption) several years ago. I no longer get along with my adoptive parents and wish to end the adoption. Is this possible?

No. Once granted, adoption is irrevocable (Civil Code, Article 359).
However, Article 345-2 paragraph 2 of the Civil Code provides two exceptions:
•    A new adoption is possible if the adoptive parents have died.
•    A simple adoption may be granted for a child already fully adopted if there are serious grounds.