Use logic, feats, and stats.
Assume firepower and shields are equalized.
The First Order has StarKiller.
The Covenant have High Charity.
The galaxy's are merged. Covenant on one side, First Oder at the other.
Both at their peaks.
-
Covenant. I'm a hardcore star wars fan but there is no way the first order would even stand a chance. The first order is significantly smaller and less powerful than even the galactic empire. The covenant would of overwhelm just by force of numbers alone. Not mention the first orders inept leadership.