Evulz rules over his dark kingdom with an iron fist... but he's one of the allies of the Heroes, and isn't that interested in conquest.
He calls himself Emperor Evulz, rules the Dark Kingdom, wears a black cloak and armor with horns and spikes, decorates everything in black and red with skull motifs, employs an army of orcs and trolls... but he's actually a fair ruler and a pretty nice guy, and the orcs and trolls get along fine with everyone else.
Evulz rules over his dark kingdom with an iron fist... but he's pretending to be one of the allies of the Heroes, and is that interested in conquest.
Evulz and his Mooks are indeed nice, but they're still evil.
Evulz rules over his dark kingdom with an iron fist... and he uses that iron fist to Poke the Poodle.
Evulz is Stupid Evil and believes that "ruling over his dark kingdom with an iron fist" entails wearing an outrageously oversized metal gauntlet and standing at the top of his Evil Tower of Ominousness with his gloved arm outstretched.
Zig Zagged: Evulz isn't always evil, but only when he needs to be or feels like it. He has Legions of Doom...all members of which have good pay and health insurance. He strictly controls all information media...but gives the population access to them for free. As a result, his kingdom is a toss-up between Utopia and Dystopia with some things being okay and others awful. And he wears the horned helmet because he just likes the look of it.
Averted: There are bad guys in this setting, but none of them qualify as an Evil Overlord.
Enforced: "We need to make the villain a plausible threat, so we're going for the whole overlord thing."
Lampshaded: General briefing the heroes about Evulz: "He's your fairly standard Evil Overlord."
Invoked: He's a political pragmatist who doesn't like drama, but knows his job ruling the empire will be easier if he takes the name Emperor Evulz and periodically oppresses the populace.
Exploited: The Hero knows that Evulz is powered by evil and hate, so The Hero uses love to defeat him.
Defied: Evulz takes over the kingdom, and his first act is to make a list titled "How To Become An Evil Overlord". He proceeds to deliberately avoid everything on that list, because "everyone knows that the evil overlord always gets overthrown".
Conversed: "I'm gonna say that the guy with the black cape and shoulder spikes is the Big Bad."
Implied: While Evulz is dark and has an Obviously Evil name plus appearance, he's never seen doing anything evil and we only have the rumors that he might be evil.
Deconstructed: Evulz takes the throne, but his reckless taxation wrecks the economy of a nearby kingdom, which immediately declares war. Another nearby kingdom is overly idealistic, and declares a war of liberation of the people. The downtrodden (i. e. disarmed) masses in Evulz's kingdom are horribly incompetent fighters even when conscripted and given weapons, and anyway as soon as they realize they're going to lose their combat tactics become "find the idealistic kingdom's army and surrender to them, they treat prisoners better than our ruler treats us". The overlord is overthrown before he's ruled for six months.