No one can defeat Atem... he is the king of games. He mastered games he didn't even know how to play at first in Yugioh season 0. Also he has the Heart of the Cards!! and friendship...
UNLESS!!! Doom takes away the Pharaoh's leather pants than he wins.... because according to Marik the leather pants are the source of his power.. XD
Doom can try cheating all he want Yugi still wins. Pegasus could pretty much see every card Yugi was going to play so Yugi just started playing cards without looking at them himself and still won. Then when Yugi wins he'll just mind fuck Dr Doom using his millenium puzzle like he did to that one guy.
Or you know Doctor doom cheats and shoots a plasma beam at his face :)
That wont work... Atem will get up because of friendship... and if this is season 0 Yami Yugi.... then he ruins Doom's life for ever, because he cheated... and he can send him to the Shadow Realm.....