Datapack
KillStreakPack
make a datapack for minecraft 26.2 that works on servers when the player kills another player (could be anyone) the player that kills the other player gains the effect speed with a maximum of the effect speed level 4 and after 10 kills the player gains the effect strenght 2 if the player dies at 10 kills they loose a level of speed and all the strenght until they get back to 10 kills, every death a level of speed is lost
data/killstreak/functions/on_kill.mcfunction
scoreboard players operation @s ks_speed = @s ks_kills
scoreboard players remove @s ks_speed 1
execute if score @s ks_speed matches 0 run scoreboard players set @s ks_speed 0
execute if score @s ks_speed matches 1 run effect give @s minecraft:speed 999999 0 true
execute if score @s ks_speed matches 2 run effect give @s minecraft:speed 999999 1 true
execute if score @s ks_speed matches 3 run effect give @s minecraft:speed 999999 2 true
execute if score @s ks_speed matches 4.. run effect give @s minecraft:speed 999999 3 true
execute if score @s ks_kills matches 10.. run effect give @s minecraft:strength 999999 1 true
execute if score @s ks_kills matches ..9 run effect clear @s minecraft:strength