I know what happens if a charcter wins a opposed challenge with deadly, but what happens if I challenge with a deadly charcter and lose does my oppenent still have to kill someone even thou they won thank you

If you have another look at the rules, you'll notice that the resolving of the deadly keyword is not dependent on who won the challenge, only one who provided more characters with the deadly keyword. So yes, if you as the attacker have more participating characters with the deadly keyword than the defender, and the defender wins the challenge, they still have to kill on of their participating characters.