I vote yes on “You are Already Dead” as a card name. It is flavorful in that it kills a damaged creature and that it implies it was easy, not even costing you a card. Although I prefer instants and sorceries to be verbs like “I shock your creature” or “I commune with spirits”, it still allows you to name the spell alone like “saw it coming.” You don’t need to say “I cast ‘you are already dead’”, you just say “you are already dead”, which is very fun.

The default is instants and sorceries are verbs.

Regarding "You Are Already Dead" and "Enormous Energy Blade", I don't know the references, but both sounds like the level of silliness I'd expect of an unset, less so of a premiere set, although Magic has overall gotten lighter in tone these past years. I don't know why those two seem weird to me, whereas "Didn't say please" and "Saw it coming" are both card names I really liked.

Just like mechanics, we like having a breadth of style with card names. Humor isn’t restricted to Un-sets.

If xenagos was a planeswalker and God, why did he not plabeswalk before dying?

I don’t think he saw it coming. Also, for some planeswalkers, planeswalking can take a lot of concentration.