Who forced General Lee to surrender ending the war?

Do you mean who was the opposing General? Or do you mean which of his own Generals talked him into surrendering?

The Union commander was U.S. Grant, although technically that army was commanded by George Meade, Grant being General-in-Chief.

Lee's men were barefoot, starving and deserting in large numbers.

Most commanders would have surrendered well before that point.

He simply gathered his Generals around him and asked if any of them thought it was possible to go on. They said it wasn't.