Doesnt seem to be firing Killed, or printing Killed
local REMOTES = ReplicatedStorage:WaitForChild("Remotes")
local Players = game:GetService("Players")
local player = game.Players.LocalPlayer or game.Players.PlayerAdded:Wait()
local character = player.Character or player.CharacterAdded:Wait()
local humanoid = character:WaitForChild("Humanoid")
player.CharacterAdded:Connect(function(character)
local humanoid = character:WaitForChild("Humanoid")
humanoid.Died:Connect(function(player)
REMOTES.Killed:FireClient()
print("Killed")
end)
end)

4 comments
I think the script is getting stuck at your player variable. You do not need to use the PlayerAdded method since a local script won't even run before the player has been added.
Is this a localscript or regular script
I dont see so much of a problem but maybe an easier way to do it is by saying the players health = 0
the classic "I don't see a problem" by skids when there are 6 problems present.