My comprehension is failing me in that last sentence by Nagato.
Is it "You kept me waiting, you idiot" or "Wait for me, you idiot"?

.....should we be worried about Enterprise there in the background?

Sigfried666 said:

My comprehension is failing me in that last sentence by Nagato.
Is it "You kept me waiting, you idiot" or "Wait for me, you idiot"?

The latter. It's the equivalent of 待たない（か）. The -ん is a negative "ん", deriving from the Classical negative -ぬ. It's like saying 知らん instead of 知らない.

If it's the emphatic/explanatory -ん (itself a contracted form of の), then it would be 待ったん（か）. One っ makes all the difference.

The "-ん" negative ending is frequently used in modern Japanese, but generally only in casual speech (it can come out as rude otherwise). Western (Kansai and some others) dialects tend to use it more.

In fiction, however, the "-ん" ending is also given to pompous (and old/venerable sounding) speakers, including those who speak in an archaic 'stage' dialect (AKA Ye Olde Butcherede Zipangese). For the latter this is further reinforced by other 'archaic' grammar constructions like -ぬ and -せん (from せぬ), and archaic-sounding vocabulary ('pronouns', plus a multitude of 'pompous' old-fashioned sounding variants of "fool"/"stupid").

AzLane Nagato speaks in this way, and uses all the above examples. Most "lolibaba" types also do, especially if they are in some position of authority.