Crossword puzzle clue "best possible ending"

Best possible ending?

Spiritual leader who said, "Be kind whenever possible. It is always possible."

It won the 2003 Tonys for Best Musical, Best Book, and Best Score

Possible tennis score before a game-ending ace

Possible URL ending

One possible ending for a boxing match: Abbr.

Capability of a system to modify its own operation to achieve the best possible mode of operation

Best possible mark