Its freakin easy.
You just use a trigger that recognizes the name of the enemy character,and if thats the right name it will trigger the win position.
If that is not what you meant:
A character can only have ONE ending.Endings can NOT be triggered by characters,but you can still make long ass cut scenes to be triggered AS a win pose.
Character specific win quotes are easy to do,just check out the latest characters since they ALL have it.
IF you want to have a win screen appear before 1.0s win screen you will have to code it as an explod with a higher sprite priority than the character