Riser is almost immune to physical attack and with ruler he cannot be harmed with magic attack so this must be battle of attrition that why take too long
Teleport to Indra, Hades, and the rest of the top 10, and Ophis, mind controlling them all to fight and kill Great Red.
Or use the memory controlling fruit to rewire Red’s mind into being a loyal minion.
“Go! Slifer the Sky Dragon! I choose you!”
Well, now just wait for the wonderful booster pack for killing the hero, right? And since he's a hero, there must be a pretty good reward, right? I wonder what he'll get?