After the wewe defeat your shadow, wewe face the 'Mysterious Warrior'. After the wewe defeat him, he gives his dying speech and wewe 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