It really is quite fascinating to me that Magellan went up against Shiryu for killing prisoners willy-nilly when he's done the exact thing several times over the course of the arc, not to mention all the times he poisoned his own men, both accidentally and not.
I suppose if I had to pinpoint the difference between them it would be that Magellan's displays of force have been in service to his authority, whereas Shiryu just likes killing people. Magellan thinks that ruling Impel Down with an iron fist is the only way to keep the prisoners in line, so he's quick to pull out the poison hydra even if he gets no personal pleasure out of it. But at the end of the day the result is the same, and if anything Magellan's poison is a crueler fate than getting your throat cut by Shiryu.











