The archenemies of Guts in Berserk perform extremely depraved deeds for their own amusement. This is without mentioning the fact that every demon was once a human, who then sacrificed something or someone dear to them to the Godhand, the primary main villains of the series in general, to become that way. Due to the depressingly harsh nature of the setting, though, only a very few actually deserve to be on this list.
Wyald is the second Apostle encountered and one of the nastiest pieces of work that Guts and company meet before the Eclipse goes down. A depraved hedonist and Serial Killer, he leads a band of mercenaries made up of the worst murderers, rapists and all around scum that Midland has to offer. Wyald is introduced in the midst of an orgy, having sex with several dozen women. As he finishes with each girl, he breaks her neck, hurls her onto a pile of bodies, and then moves onto the next one, gloating about how his motto is "Excitement and Enjoyment." This sets the tone for the rest of his appearances, which show him to be a walking, breathing, raping machine. When he and his knights come across a young family, including a mother and several children, that have aided the Band of the Hawk that they have been hired to track down, they proceed to rape and murder everyone, including the children. This is followed by dismembering their bodies and carrying them naked on poles into battle with the Hawks, who are all horrified at the sight. He demonstrates an utter disregard for his men's lives, frequently triggering traps and getting them killed, solely so that he can laugh at their deaths. After transforming into his true shape, of a fifty foot tall gorilla with a three foot thick spiky penis, he attempts to rape Casca with it, bragging that she'll "feel like a virgin again" as it rips her in two. Even his own men, the aforementioned worst scum of the kingdom, follow him mainly because they are utterly terrified of him.
Ganishka, the Emperor of Kushan, became insanely paranoid, when his mother tried to poison him for his younger brother to become the heir, only for the latter ones not to survive. His paranoia got to the point where his own son tried to kill him out of fear he would see his son as a threat. After accepting the Godhand's offer he has become a near-perfect example of The Caligula, which shows in mass executions, ethnic cleansing, using conquered populations as human shields or cannon fodder for his armies, attempting to rape the captive princess Charlotte and suspending women over a pool filled with hungry crocodiles, dropping thousands of pregnant women into cauldrons with stitched-together Apostles to turn the unborn babies into half-human demons that rip apart their mothers upon birth. Grandiose, megalomaniacal, and obsessed with his position as The Emperor, Ganishka revels in being as evil as he possibly can be.