Well, I think the author's intention of the last duel of DM was to prove Yuugi surpassed Atem without they knowing it. Since, Atem did go serious mode and did all he can and Yugi was countering Atem's moves one by one. Also their conversation after the duel make me think the author is trying to demonstrate that Yugi did indeed surpassed Atem. :S
Did Yubel really did all the things in season 3 of GX because of her twisted definition of love? Or, was it because her loneness? (or any other reason)