Definitely think it looks better without Rhonin-- it puts the focus more on Nell's emotional state and actions, which makes the story feel tighter. In the previous version it was a bit unclear what Rhonin was doing, or how he was relating to Nel or the bomb.
Great use of color. It gives Nel dimensionality, and helps suggest that he's moving fast. It also suggests that he's not fast enough, since the violet ring looks like the fringe of the initial blast pulse.
Nel also looks great. His musculature and the depth of his chest makes him look powerful, and it's clear he's throwing his incredible strength behind his attempt to grab the bomb... and that it won't be enough.
Perhaps the one thing that bugs me is Nel's eyes. His eyes are looking down and to the left, which is out of frame. Even in the version with Rhonin Nel's not quite looking at Rhonin-- he's really looking offscreen. This makes the focus of Nel's attention a bit unclear.
It might be a bit stronger emotionally and in terms of storytelling if Nel were looking at the bomb. In this version of the image the bomb is the only other character present, and it's ultimately the thing that is driving Nel's behavior and his mental and emotional state here. Having him looking at it should make it more obvious that he's trying to catch the bomb, and it may make his emotional state seem more intense by explicitly connecting his desperation and despair to its cause.