var col = from le in mylist
group le by le.X into g         
orderby g.Key descending
select g;

var colGrouped = from le in mylist
group le by le.X select le;
 
var colOrdered = from colGrouped ..... orderby...

public class Invader
    {  //see directionandtypeenum.cs for Type definition
        private const int HorizontalInterval = 10;
        private const int VerticalInterval = 25; //40;
 
        private Bitmap image;
        private Point location;
        public Point Location { get { return location; } }  //changed this to make life easier
        public Type InvaderType { get; private set; }
 
        public Rectangle Area { get { return new Rectangle(location, image.Size); } }
 
        public int Score { get; private set; }
        public Invader(Type InvaderType,Point location,int score)
        {
            this.InvaderType = InvaderType;
            this.location = location;
            this.Score = score;
            image = InvaderImage(0);
        }
 
        public void Draw(Graphics g,int animationCell)
        {
 
            g.DrawImage(InvaderImage(animationCell), Location);
        }
 
        public void Move(Direction direction)
        {
            switch (direction)
            {
                case Direction.Down:
                    location.Y += VerticalInterval;
                    break;
                case Direction.Left:
                    location.X -= HorizontalInterval;
                    break;
                case Direction.Right:
                    location.X += HorizontalInterval;
                    break;
                default: break;
 
            }
        }
 
        private Bitmap InvaderImage(int animationCell)
        {
            return (Bitmap)Properties.Resources.ResourceManager.GetObject(InvaderType.ToString().ToLower() + (animationCell+1).ToString());
 
        }
    }

       private void FireInvaderShots()
        {
            if (invaderShots.Count <=2)
            {
 
                var Column = from inv in invaders
                             group inv by inv.Location.X into g
                             select g;
                //into invadergroup             
                //orderby invadergroup.Key descending
 
 
 
 
                var cols = from v in Column
                            where v.ElementAt(v.Key).Location.Y == v.ElementAt(v.Key).Location.Y.Max()
                            select v;
 
                List<Invader> col = new List<Invader>();

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Linq.Expressions;
 
class MainApp
{
    static void Main()
    {
        List<MyData> items = new List<MyData>();
        items.Add(new MyData("A", "1"));
        items.Add(new MyData("A", "2"));
        items.Add(new MyData("B", "3"));
        items.Add(new MyData("A", "4"));
 
        var result = from all in items group all by all.State into grpResult orderby grpResult.Key descending  select grpResult;
 
        foreach (var t in result){
            Console.WriteLine(t.Key + " " + t.Count());
        }
    }
}
public class MyData{
    public string State { get; set; }
    public string City { get; set; }
    public MyData() { }
    public MyData(string _state, string _city){
        State = _state;
        City = _city;
    }
}

 var Column = from all in invaders group all by all.Location.X into grpResult orderby grpResult.ElementAt(0).Location.Y descending select grpResult;
 
foreach (var v in Column)
Console.WriteLine(v.ElementAt(v.Count()-1).Location.ToString());