Kuurth is amped by Cyttorak and Cul
Doomsday is strongest version.
Fight starts on Oa with constant periodic attacks from Green Lanterns. Kuurth and Doomsday just want to attack each other and attack GLs only when they interfere.
If fight continues then, Mogo joins, then Seven Lantern Corps join. If fight still continues, then Galactus and The Spectre start blasting them.
Who gets KO/killed first?