The situation is a gunman was shooting at the MC, but a transmission through his radio told him to desist. How would he say "Whatever you say, boss." Assuming that the gunman is a gritty person that is disappointed by the order, but not enough to disobey it, or simply doesn't care either way because it's just a job to him.
Maybe those words are sufficient without an adverb. If not, his subsequent action, or comment after he gets off the radio may indicate his reaction.
"He said with a sigh." That would show his disappointment with the order. I'm trying to think of a good adverb, but am not coming up with anything. Will come back if anything hits me.
These days, he would just say, "Copy that". If you need the reader to know he doesn't like the order, maybe "Copy that", he sneered.
Disparagingly... but that's a bit of a mouthful. Scathingly? With contempt? Scorn? Disdain? Derision? That is, if you really need a word and not an action... e.g. spitting, or taking his time to fully comply.
Maybe just write in something beforehand. I like to work in a bit of context and description and then let the dialogue shine without any adverbs. Not that I hate them I just don't find any use for them after I build up the scene or context. There was a glint in his eye and a small sneer on his lips as he toyed with the gun. Wheels in his brain going round and round behind that hard face with the idea so clear in that glint; pretend you didn't hear the order. He lowered the gun. "Whatever you say boss." - example.
Often 'received' or 'affirmative' are used too, following the proper radio communication protocols (The Royal Signal training I did highlighted brevity* as an important rule, although that doesn't always help in a dramatic setting!) 'Tersely' would imply displeasure; "brief and direct in a way that may seem rude or unfriendly". * ie, at work I say simply 'send' rather than 'send me your message'. It's more concise, and has a clear meaning in the context, but rather sparse. Of course, people don't always follow proper protocol and what is said over the radio waves, and I'm sure it's as true for the Bravo Zero Ones as anyone.
I think something like this could work. Set up the mood of the character, show what he's like, and the reader will hear the "right" tone of voice (whatever feels right to them). I'm reading Clavell's Shogun right now, and I'm so envious of his ability to write such dialogue that I keep hearing the tones, nuances, everything while I read it. They might not be exactly what he heard while writing, but I doubt it matters. It's just so lively and real.
