i know you won't read all this but
i looked at the deck source and found some issues with your leaderboard:
1. your leaderboard button contains this rule:
[When this is created
Repeat every 0 seconds
Save variable (none) to the leaderboard]
the problem is that it isn't saving any variable. try changing it so it saves $kills.
2. the blueprint called Wall 23 (the one that triggers the text box "Why you kill green:[") contains this rule:
[When this collides with tag #character
Modify variable $kills to 1 (relative)
Play sound 0 4 tone at rate 1, volume 1
Destroy this actor]
the problem with this rule is that it only triggers when the blueprint collides with tag #character. there is nothing in this deck that uses #character. rather, 'green' uses #thing, so change it to that.
3. make the variable $kills persistent per player. this can be done through the cogwheel at the top when you're editing your deck.
but if you did read all this, thank you :)