void UpdatePlayerUI(BasePlayer player)
{
var container = new CuiElementContainer();


var Box_1 = container.Add(new CuiPanel
{
Image =
{
Color = "1 1 1 0.2691276"
},

RectTransform =
{
AnchorMin = "0.73125 0.8972222",
AnchorMax = "0.9953126 0.9444444"
},

CursorEnabled = false
});

var Box_2 = container.Add(new CuiPanel
{
Image =
{
Color = "1 1 1 0.2691276"
},

RectTransform =
{
AnchorMin = "0.73125 0.8379627",
AnchorMax = "0.9953125 0.886111"
},

CursorEnabled = false
});

var USER_1 = container.Add(new CuiLabel
{
Text =
{
Text = "USERNAME 1",
FontSize = 14,
Align = TextAnchor.MiddleLeft

},

RectTransform =
{
AnchorMin = "0.7359375 0.9083333",
AnchorMax = "0.9291667 0.9379629"
}

});

var USER_2 = container.Add(new CuiLabel
{
Text =
{
Text = "USERNAME 2",
FontSize = 14

},

RectTransform =
{
AnchorMin = "0.7348959 0.8509259",
AnchorMax = "0.9296875 0.8722222"
}

});


var USER_SCORE1 = container.Add(new CuiLabel
{
Text =
{
Text = "5",
FontSize = 14,
Align = TextAnchor.MiddleLeft

},

RectTransform =
{
AnchorMin = "0.9760417 0.9111109",
AnchorMax = "0.9895833 0.9333332"
}

});


var USER_SCORE2 = container.Add(new CuiLabel
{
Text =
{
Text = "4",
FontSize = 14,
Align = TextAnchor.MiddleLeft

},

RectTransform =
{
AnchorMin = "0.9760419 0.848148",
AnchorMax = "0.9875001 0.8777776"
}

});


var TXT_HDR = container.Add(new CuiLabel
{
Text =
{
Text = "Score",
FontSize = 20

},

RectTransform =
{
AnchorMin = "0.8484375 0.9472222",
AnchorMax = "0.9005209 0.9833333"
}

});

CuiHelper.AddUi(player, container);
}

void UpdatePlayers()
{
foreach(BasePlayer player in BasePlayer.activePlayerList as List<BasePlayer>)
{
CuiHelper.DestroyUi(player, "container");
UpdatePlayerUI(player);
}
}​

Code above is my ui, which works perfectly excecept when I want to update the player score the ui updates but it does not destroy the old one. So it constantly overlaps the old ui w/ the new 1. I call UpdatePlayers(); whenever the player dies but it isnt shown above. I am pretty sure I am doing something wrong with CuiHelper.DestroyUi(player, "container"); I just don't know what it is

You are destroying a CUI named "container" but the CUI you're sending does not have that name.

Look at the parameters of the CuiElementContainer.Add method, the third argument is the name.  You will want to specify the name (when you add the CuiPanel) in order to destroy it later by that same name.

https://github.com/theumod/uMod.Rust/blob/c86526775599536fc3a89bb1e219475fcdb4b29e/src/RustCui.cs#L63