(Tried both gamemodes)
Command blocks are in a 3x3 grid with redstone on top of all of them, activated by a pressure plate.
Commands used:
/scoreboard objectives setdisplay sidebar
/scoreboard objectives setdisplay list
/scoreboard objectives add deathcount deathCount Deaths
/scoreboard objectives add totalkills totalKillCount TotalKills
/scoreboard objectives add playerkills playerKillCount PlayerKills
/scoreboard players set @p killtest 0