Jesse Custer has a power that "rivals the power of God" (as the angels Fiore and DeBlank said). The power could be summarised as "do EXACTLY what I've said", which from the meta point of view is neither godlike powerful nor original - in other comic books there are lots of characters who can do similar things (e.g. Kilgrave from Jessica Jones, Silverfox from X-Men O:W who could do that via touch, or to a certain degree any telepath like Charles Xavier or Martian Manhunter from DC) - but can be seen as "godlike" in a world without magic or superheroes.
But then Jesse in anger accidentally sends a kid to Hell, by shouting those exact words. Fiore also seems to find tranquility after death when Jesse tells him to "find peace".
So what exactly are the limits of this "godlike" power? Is it just Kilgrave-like "overwriting" of free will or is Jesse a reality warper* able to alter physical world, that could for example tell someone to "grow wings", "be immortal", cure Cassidy from vampirism or (since his power seems to work on at least certain animals) tell a dog to "evolve into humanoid"?
In example: Jesse told Cassidy to fly - Cass jumped and hit the wall after which Jesse ordered him to stop. Does it mean that
a. Cassidy just tried to follow the order but couldn't
b. Cassidy COULD fly for that brief moment** until the wall stopped him and Jesse told him to stop?
If there are differences between his power level between the TV show and the comic I'd ideally like to see an answer relating to both.
* TV Tropes warning!!!
** We can safely assume that vampires can't fly - when Cassidy jumped from the plane he crashed pretty badly on the ground