Isshōmaru Ureshii/Tropes

A-G
Darker and Edgier: At first, Isshō was created just to be Darkrai's obligatory trap character, and mainly used as an excuse to get some easy access to Lightning-Fire Dragon Slayer, back when he was very bad at what he does. As of Isshō's revamping, Darkrai has abandoned the Slayer Magic, given Isshō a less fanservicey (but still very feminine) appearance, expanded on his backstory to include a very nihilistic view of humans, and made him so obsessed with staying alive that he willed himself back to life.