Spencer

In all out war, no distractions or alliances, those are definitely not all making the cut.

The Terran marines were actually originally intended to be space marines, look into it on your own time if you're interested but long story short, the first Starcraft was supposed to be a 40k game, so I give them fair odds.

The UNSC, not a chance, the Spartan ll's are pretty great, but considering their limited numbers even compared to space marines, they would need way too much plot armor to be taken seriously.

The Covenant are somewhat comparable to the Tau, in that they can survive in the same galaxy, they could even fight them on occasion, but the Tau are kept alive by the fact that there are far bigger threats in the area to distract from a detailed extermination, without that kind of protection the Covenant lose.

The Cylons are the hardest for me to judge, they would likely have a strategic advantage, but unless given time to upgrade their bodies, even the most threatening Cylon is kinda a joke to a space marine.

I'm fairly confident in my assessments, this is one of the rare few times I'm pretty well informed on all the factions involved, but if I missed something I'm sure I'll hear about it.

Present me with a petition to keep the bans and I'll sign it.

Until cEDH becomes it's own separate format, there will need to be occasional bans like this one to maintain the original casual nature of commander.