It isnt a must but...We need to see your leaderboard trigger(s) first.
Boss
Events
Unit - A unit enters <region>
Conditions
(Unit-type of (Entering unit)) Equal to <unit>
Actions
Set Lives = (Lives - 50)
If (All Conditions are True) then do (Then Actions) else do (Else Actions)
If - Conditions
Lives Equal to 0
Then - Actions
Player Group - Pick every player in (All players) and do (Game - Defeat (Picked player) with the message: Defeated! )
Else - Actions
Do nothing
Boss
Events
Unit - A unit enters <region>
Conditions
(Unit-type of (Entering unit)) Equal to <unit>
Actions
Set Lives = (Lives - 50)
Leaderboard - Change the title of (Last created leaderboard) to (Lives back: + (String(Lives)))
If (All Conditions are True) then do (Then Actions) else do (Else Actions)
If - Conditions
Lives Equal to 50
Then - Actions
Player Group - Pick every player in (All players) and do (Game - Defeat (Picked player) with the message: Defeated! )
Else - Actions
Do nothing