I don't know why this hasn't already been made, but here goes...
What's The Work[]
Super Smash Bros. Ultimate is the most recent installment of the acclaimed Super Smash Bros. franchise. It's also the installment that introduced possibly the most powerful Super Smash Bros. villains yet: Dharkon and Galeem. Dharkon and Galeem have been locked in conflict prior to the game itself. Now "why not propose Galeem also in a different blog?" Because it's possible that Galeem was only trying to protect the Super Smash Bros. verse from Dharkon by conquering it, but decided to take pretty extreme measures and therefore lost its way.
Who is He/What Has He Done[]
It's not explained how Dharkon came into being, as the game focused on the conflict between Dharkon and Galeem, and not how they came into being in the first place.
Dharkon, despite being one of the main antagonists of Super Smash Bros. Ultimate, does not appear in all trailers/promotional material for all I know, and also throughout the first third, the "World of Light stage" of the game, and is not even mentioned up until his big reveal. The only hint we get about the very existence of Dharkon before the reveal is in the main theme for the game, Lifelight, where its lyrics at one point mention a "fading sun" rising and "glimmering shadows".
When Dharkon does show up and ambush Galeem after Galeem is defeated by the fighters, however, it rocks a pretty cool design and does it all with great fanfare. Galeem's army of Master Hands, weakened from battling the fighters, is unable to stand up to Dharkon's fresh-out-of-the-farm army of Crazy Hands and Galeem quickly flees once it realizes it is in an unwinnable battle.
After that, Dharkon basically took over the puppet fighters and spirits Galeem was using until it got defeated by the fighters (karma), after which it created a red portal and fled into it, before Galeem appeared and quickly dove down into the portal after Dharkon (more karma). The final stage is the stage where Dharkon and Galeem are shown in full-scale battle with each other, and the fighters defeat both their armies and free individual Master Hand and Crazy Hand, who quickly team up to shatter Galeem's and Dharkon's conflicting waves of energy.
At this point, the game branches and becomes a "Choose Your Own Adventure" format, leaving Dharkon's fate in your hands. If Dharkon is defeated, Dharkon is killed by Galeem, but if Galeem is defeated, Dharkon kills the fighters and impales Galeem with chains of darkness, before essentially leaving Galeem to die. It is possible, however, to defeat both Galeem and Dharkon, after which Galeem and Dharkon fall into the sea and explode.
Mitigating Factors[]
Zero. He did not display any mitigating factors in his entire time on screen.
Heinous Standard[]
Not only does Dharkon kill the fighters and possibly all life in the universe, he also, instead of killing Galeem, impales him with chains of darkness and then just leaves him there. Now, due to the light being seemingly forcibly sucked out of Galeem and the fact that Galeem and Dharkon are essentially mortal enemies due to their conflicting natures, this is likely Dharkon torturing Galeem and making sure that Galeem dies in the most painful way possible, which is an act of sadism and cruelty.
Final Verdict[]
I proposed Dharkon due to it being an embodiment of chaos and darkness, seeking to do nothing but kill and destroy, and wanting the Super Smash Bros. verse to drown in its darkness without having any reason or even delusion for doing so and showing absolutely no redeeming qualities. Oh, and did I mention that it is also a sadistic and cruel being as shown in the Dharkon ending?