After the 你 defeat your shadow, 你 face the 'Mysterious Warrior'. After the 你 defeat him, he gives his dying speech and 你 later find Marian returned to life. The Nes & PC Engine version feature this ending.
The first Double Dragon game, please note that i'm not going to post the nes version here becuase it was infamous for lacking co-op play, making Jimmy a boss & an awful vs. mode