Death counter doesn't increase properly? [SOLVED]

For first, use game.Players.PlayerAdded not game.Players.ChildAdded and use player.CharacterAdded not player.Changed

remember :connect is deprecated. use :Connect

Example:

game.Players.PlayerAdded:Connect(function(player) -- Detect player join
	print("Player added")
    player.CharacterAdded:connect(function(char) -- Detect char spawned
		print("Character added")
        char.Humanoid.Died:Connect(function() -- Detect humano died
            print("Human died")
        end)
    end)
end)

Here is fixed script:

game.Players.PlayerAdded:Connect(function(player)
	
	-- Detect for leaderstats
	
	local leaderstats
	
	if player:FindFirstChild("leaderstats") then
		leaderstats = player.leaderstats
	else
		leaderstats = Instance.new("Folder")
		leaderstats.Name = "leaderstats"
		leaderstats.Parent = player
	end
	
	-- create deaths value
	
    local deaths = Instance.new("IntValue")
    deaths.Name = "Deaths"
    deaths.Parent = leaderstats

	-- detect character added.

    player.CharacterAdded:Connect(function(char)
	-- detect humanoid died.
        char.Humanoid.Died:Connect(function()
            deaths.Value = deaths.Value + 1 -- add 1 value to values
        end)
    end)
end)

Wiki pages:

CharacterAdded

PlayerAdded

Humanoid.Died

Hope it helped :)