It's difficult to determine the "best" anime girl character as it is subjective, as different people have different preferences. However, here are a few highly-regarded anime girl characters that are often mentioned as some of the best:
Sailor Moon (Sailor Moon) - Usagi Tsukino, also known as Sailor Moon, is a kind-hearted and determined young girl who fights for love and justice. She is known for her strong sense of duty and her ability to inspire others.
Bulma (Dragon Ball) - Bulma is a brilliant scientist and inventor who becomes a close ally of Goku and the rest of the Dragon Ball cast. She is known for her intelligence, resourcefulness, and her strong will.
Mikasa Ackerman (Attack on Titan) - Mikasa is a skilled warrior and member of the Survey Corps, who is fiercely loyal to Eren Jaeger. She is known for her strong sense of duty, her fierce determination and her exceptional fighting skills.
Kagura (Gintama) - Kagura is a skilled swordsman and member of the Yorozuya team. She is known for her strength, her determination, and her ability to inspire others.
Akame (Akame ga Kill!) - Akame is a skilled assassin and member of the Night Raid organization. She is known for her strength, her loyalty, and her ability to remain calm in the face of danger.
These are just a few examples, and there are many other amazing anime girl characters out there, each with their own unique personality, abilities, and stories that make them stand out.