The Magnificent Bastard is intelligent, capable, supremely competent, and always in control. He can be playing everyone from both ends, or making it up as he goes along with such consummate skill he gets away with it. He might be cynically exploiting all around him for his own ends, or persuading everyone to do everything for him. He might be a lying sneaky bastard playing everyone for his own selfish ends, but he goes about it with such breathtaking skill and panache you admire him for it. Above all else, what defines a Magnificent Bastard is his ability to evoke not just amazement, but grudging admiration, from friend, foe and audience alike.
They are brilliant and utterly devious, always coming with backup strategies so that they win every time, and not to mention they're smooth operators. They always know exactly what to say and never lose their cool (sometimes unless if it's in certain times when something goes wrong for some of them). The Magnificent Bastards have goals that they don't stop until they accomplish, plus they are charismatic, and almost all of them are often charming. Even at their darkest hours, they have traits that one can't help but admire.
A Magnificent Bastard can be aligned with any side - this category of course deals with the villainous kinds of Magnificent Bastards. It's also possible for Protagonist Villains to be Magnificent Bastards, but it's quite rare to find a Magnificent Bastard in one. Sometimes, a villainous Magnificent Bastard can fall short due to being so arrogant, and sometimes, when said villain goes too over-the-top to be believable, he becomes a Villain Sue. Despite that, said character isn't too likely to be a complete idiot at best.
MB's are often but not always recognized for thier taste for and indulge in luxurys such as beautiful women, cars, cigars, jewlery etc.
MB: I know. Too bad you'll never know what it's like.