I requested an Undo, and my opponent decided to not respond to it and just wait it out.
I kept trying to talk to him in the chat, but he ignored me.
It was really boring, and I hate having to wait 3 entire minutes before I can make the opponent resign.
But imagine my surprise when, after 3 minutes were up, the game informed me that **I** resigned!
This was really frustrating. Adding insult to injury, it wouldn't even give me the "Continue With Bots" option, but that's another story.
TL;DR if someone requests an undo, you might be able to win just by waiting them out and then forcing them to resign.