options:
p: &8[&eStats&8]
p3: &8[&3Stats&8]

variables:
{kills.%player%} = 0
{deaths.%player%} = 0

on death:
add 1 to {kills.%attacker%}
add 1 to {deaths.%victim%}

command /stats [<text>]:
trigger:
if arg 1 is not set:
message "&7---&c[&6stats&c]&7---"
message "{@p3} &7Kills&8: &a%{kills.%player%}%"
message "{@p3} &7Deaths&8: &c%{deaths.%player%}%"
message "&7---&c[&6stats&c]&7---"