Reconstruct the sentence. The word you are looking for (limp and unresponsive both work quite well) is describing the behavior of the body, not the nudge.If you rephrase this with a phrase, you'll see this quickly enough.
A nudge with the toe of his boot--which brought no response--was convincing enough.
In this sentence, there is no clear indication why the nudge brought no response. I could be that the creature was dead, but then again, it could equally be the fault of the nudge, perhaps he didn't nudge hard enough or maybe his boot was too soft.
You can see that Gwalchmai and Fire-Bringer didn't even get what you were looking for, they both suggest adjectives (and an adverb) that describe the nudge, not the response.
But this is all rather out of place. The reason that you nudge a dead body like that is not because you expect a response. If the creature is unconscious or fiegning death, there won't be one. The reason you nudge the body is because a dead body feels completely different from a live body, particularly the abdominal wall. In a live body, there will be detectable muscle tension. In a dead body...not so much. Of course, with the use of a muscle relaxant or certain forms of meditation, this degree of relaxation can be imitated. But the fact remains...limp is the word you want.
Just apply it to the body, not his nudge.