The "Tournament Ends" trigger doesn't provide additional information, such as <name>. Perhaps it should.
In the meantime, you probably want to use the "A player busts-out" trigger, set the conditions to:
players = 1
And then use the <hitman> token to identify the winner, like this:
Congratulations <hitman>!
You'll want to move this event above any other events that use the same "A player busts-out" trigger, since this one is very specific and will be ignored until the final bust-out.