execute if score @s kill_streak_timer matches 1 run scoreboard players set @s kill_streak 0

#execute if score @s kill_streak matches 3.. run particle minecraft:flame ~ ~1 ~ 0.25 0.5 0.25 0.025 1
execute if score @s kill_streak matches 5.. run effect give @s minecraft:speed 1 0 true

scoreboard players remove @s kill_streak_timer 1