Canon Sue: Every third character is said to be this.
Complete Monster: Bidithal is an elderly member of the rebellious army the Whirlwind and its most powerful High Mage who gets away with his atrocities due to his power and high position. He has a disturbing taste for little girls that he rapes and performs female circumcision on. In his darkest act, Bidithal captures the adopted daughter of the Whirlwind's leader, Felisin the Younger, and rapes her. He tells her he will "drink all the pleasure from your precious body, leaving naught but bitterness, naught but dead places within." Even the barbarian Anti-Hero Karsa Orlong finds Bidithal an utter blot on humanity as a whole and relishes a chance to force Bidithal to choke on his pleasure.
Cult Classic: Opinions abound that it will never reach mainstream success circa A Song of Ice and Fire because the depth and complexity that makes it great is alienating to casual readers, and cannot be translated to other mediums.
Crazy Awesome: Karsa Orlong, Iskaral Pust, Tehol & Bugg, Second Seguleh, Bauchelain and Korbal Broach, probably all sapers...
As we see in The Crippled God, after becoming Master of the Deck, Captain Ganoes isn't afraid to come to talk to dangerous enemy commander, just to see what person she is, and piss her off just by talking... and he gets away with it!
Cotillion and Udinaas are quite popular. The former quite openly, the latter having a cult following little talked about.
Torvald Nom, who only shows up briefly in House of Chains, has gained a lot of popularity, spawning forum rants about how badass he is . In Toll the Hounds, be becomes an Ascended Extra, with his own minor storyline.
Fandom Berserk Button: The Malazan Book of the Fallen was written by Steven Erikson, not Steve Erickson, Stephen Erickson, or even Erik Stevenson. To add insult to injury, a good number of people who cannot be bothered to take a look at the cover are those who claim he cannot write worth a damn.
Rhulad Sengar. Yeah, he's technically an Evil Overlord and has done some inarguably bad things- but just look at the rest of this list. You've got to feel sorry for the poor guy. He needs a hug. And possibly, a therapist.
A particularly obvious example, Sirryn Kanar in Reaper's Gale seems to exist solely to cross it repeatedly.
Mallick Rel convincing High Fist Pomquarl to abandon Fist Coltaine to die outside the walls of Aren. Particularly vile since Coltaine was less than five hundred metres away, the garrison was more than strong enough to rescue him and Coltaine had just spent the last few months leading 30,000 Malazan refugees across a desert to safety.
If that's not bad enough, Rel crosses it again only a few pages later when he betrays Aren to the Army of the Apocalypse, resulting in 10,000 soldiers being crucified and left to die.
And the absolute worst part? He's a Karma Houdini, and when his plan fails he convinces everyone that he was the hero who defended Aren and that Coltaine and the Wickans were the true enemy. After Laseen's death he becomes Emperor of the entire Malazan Empire.