So the character in question is widely regarded as one of the most hated in all of anime…

It’s a reference to a particularly shitty character from Full Metal Alchemist

So there was this anime called 'fullmetal alchemist'.

The first scene is the then pre-teen main characters, two orphaned brothers, dismembered and splattered around the room after defying the laws of man and god in an attempt to resurrect their mother with illegal magic (the illegal impossible magic of the settings chemistry wizards is just organic chemistry. Organic chemistry is illegal and maybe cursed or ontologically evil or something) that went horribly wrong. It then cuts to a couple years later where the protagonist (now 14, and only diagetically glossing over the 'child soldier' of it all, as the absolute ruler of their vaguely Germanic central European military dictatorship is kind of a fatherly figure) with half his limbs prosthetic and his younger brother, a disembodied spirit bound to an old suit of armor, are working as military wizard-engineer maybe-counterintelligence are dismantling a cult in a city the state did some atrocities to a while back(also not glossed over. Lots of orphans, the local lady their dealing with us trauma-mute), and being kind of unnecessarily shitty about it. the audience finds out its part of a bigger conspiracy, and by the end of the episode a shapeshifter comes into town and replaces the cult leader they had exposed as a fraud and killed (claiming he was an imposter) the moment our heroes* leave.

This guy is from the episode where it becomes clear that the general tone of the show might be a little darker than previously suspected.

Satan asked the question without realizing who he was talking to. Shou Tucker's response made him realize just who he was, and he was so bad that he needed to contact god for help.