King Boo and Luigi - My old archenemy (A Luigi's Mansion Comic Dub)

His Personality:

King Boo is shown to have a deep hatred for the Mario Bros. He claims this is because of the trouble the duo has caused him in the past, presumably meaning all the Boos the Mario Bros. defeated, as King Boo had not been in any games prior to Luigi's Mansion. His hatred grows towards them in later games, especially Luigi after the latter defeats him in Luigi's Mansion and subsequent sequels. King Boo especially seems to dislike Luigi; childishly insulting him in the Luigi's Mansion games and insisting on racing against him in Mario & Sonic at the Olympic Winter Games, fully aware of how afraid Luigi is of ghosts.

He says that he fears nothing except the Poltergust 3000, although in Super Mario 64 DS he admits that Wario's face scares him, rendering the previous statement a generalization. In the Mario and Sonic series, he has a superiority complex and is quite prideful. In Mario & Sonic at the Olympic Winter Games, he claims that he is unbeatable at the Alpine Skiing events. In Mario & Sonic at the London 2012 Olympic Games, he claims to have beaten Mario before.

King Boo loves to scare and toy with his opponents, rather than defeating them quickly. He chose to use his powers to blow Luigi back to the foyer instead of trying to finish him off while at maximum power, and enjoyed watching Mario struggle from within the painting he was trapped in, stating Mario's desperate attempts to break free were "satisfying."

Despite his huge size and immense power, he still covers his face in fear when looked at, much like a normal Boo, showing that he still has a shy nature like his minions; however, also like a normal Boo, he attacks when his foe's back is turned. King Boo has a distinct cackle, which is significantly lower in pitch than other Boos. He also has an echo in his roar.

King Boo actually considers his Boo minions as friends and cares for them. This is shown in Luigi's Mansion where he goes to free Boolossus after he is captured by Professor E. Gadd, and when he threatened to hurt Paper Mario if the Mario Brothers dared to hurt his Paper Boo minion in Mario & Luigi: Paper Jam. He also has good chemistry with the playable Boo in the Mario Baseball series. In Mario Super Sluggers, King Boo says that he finds little Boos cute.

After breaking out of the portrait he was placed in at the end of Luigi's Mansion, he displays a complete disregard for anything that interferes with his revenge and displays several sociopathic traits: including a disregard for others' well being, and at one point nearly causes the world itself to collapse. Additionally, he no longer cares about the Boos, even calling them useless in Luigi's Mansion 3. He does not seem to care for ghosts that are not Boos, instead using them in his plans as tools rather than subjects. Even Hellen Gravely, a ghost who adores him, is seen as nothing more than a pawn and at best someone to whom he is indifferent. Professor E. Gadd comments on how King Boo redecorated the Treacherous Mansion to make it scarier. He also goes into fits of rage when his plans do not go the way he wants. At least in Luigi's Mansion: Dark Moon, King Boo also has a bit of a sarcastic demeanor as well, as when formally revealing himself to Luigi before fighting him, when referencing his earlier defeat at the hands of Luigi, he says "Good times" over the recollection of the event despite obviously being angry and vengeful over the earlier defeat. In Luigi's Mansion 3, King Boo impersonates Mario and Luigi's Italian accent saying, "It's-a me, King Boo!" and uses false comfort towards Luigi. Also in said game, in addition to his relatively increasingly more vengeful and anti-social nature, he is also shown to have a degree of cunning, as it was strongly implied that he deliberately had Hellen Gravely guard only Mario's portrait specifically because he anticipated that Luigi would ultimately defeat her, and used Princess Peach's portrait as bait to draw out Luigi alongside Mario in order to recapture all the portraits, with him very narrowly failing in this endeavor.

Try to Think On what he might sound Like from the Actual Games!

Ref: https://www.youtube.com/watch?v=oiU3tLdliVw