Odion's highest defense monster is a Giant Axe Mummy with 2000 Def. However, it can't do anything after you special summon your Gate Guardian. You can check more details and information regarding the deck by clicking the link below!
Summon the unhappy girl, or rai-mei if you don't have her, and pass the turns to stall the duel until you can perform the gravekeeper vassal and union attack combo. Once you summon the unhappy girl, set rai-mei again once you have enchanted javelin to raise your LP. This will make sure Odion won't attack, otherwise pumpking with castle of illusions to deal more than 5000 damage with 3 monsters.
you don't have to attack his mummy over and over. If you hit with unhappy girl once he will flip down yes but it's still locked (that happend with me last time i checked, don't know if any update has changed anything).