That has nothing at all to do with the trope, read the trope description.

Embarrissingly, I just got suspended again. But just out of curiosity, wasn't Palpatine from Star Wars a Smug Snake like the description of Smug Snake says? Like overconfidence?

It depends on what you're going by. Palpatine as Darth Sideous is widely regarded as a Magnificent Bastard. As Emperor, though, he was alot more overconfident and it led to his downfall.

Jordan said that Ursula from The Little Mermaid and Jafar from Aladdin has nothing to do with trope. He's right about Ursula, but I just realized that in The Return of Jafar, Jafar sang the song "You're Only Second Rate". Wouldn't that be considered overconfidence? Or would he be a Magnificent Bastard? After all, his overconfidence ("I'm all-powerful") as a genie led to his destruction after he put Aladdin and his friends in danger by creating a fissure in the ground. At least that's the way I see it. I'm suspended from editing for a while, so if it does apply, I think a troper other than myself or a mod should edit it back in. If not, than I think someone should put him in Magnificent Bastard if he's not in there or which ever trope(s) applies, or both if both tropes apply. I also think that Palpatine in Return of the Jedi should be put in Smug Snake because Luke Skywalker himself said he was overconfident.

While most Smug Snakes are overconfident, I don't think overconfidence in itself qualifies one as a Smug Snake as it's also a trait of most magnificent bastards.

Whether a villain seems like a Magnificent Bastard or a Smug Snake should be more a matter of author intention rather than how the fandom sees them. They're almost two sides of the same coin - a Smugsnake can have successful plans and chess-playing ability just like a Magnificent Bastard can have an amount of egocentrism.

The whole point is a Smug Snake is more of a straight villain while a Magnificent Bastard is almost written more as an Anti Villain by intent. If one comes off as the other then it's just bad writing.

MB's are often overconfident but they're very rarely arrogant to the point where it's a handicap. That's the main difference between a genuine MB and a "high-functioning" Smug Snake: the latter is very, very good at what they do, but they're not as good as they think they are (in fact it would be almost impossible for anyone to be as good as they think they are) and it leads to their defeat. See Light Yagami, Cutler Beckett, and Frank from Criminal Minds for excellent examples of this character types.

When it comes to personality, the Smug Snake is typically written to be more repellent, whereas the MB is meant to be awe-inspiring. Also, Smug Snake's seem to be a little lacking in The Trickster department: they can create a great plan, but often seem to have trouble modifying them.

With regards to the Palpatine example, one could argue that he is a Smug Snake in Return Of The Jedi. He doesn't really do anything to win the audience's respect, and is played as a cackling mad, arrogant, slimy Sorcerous Overlord throughout. It's only the prequel trilogy that established his MB status.

It just seems that the trope has decayed into "an evil Ted Baxter who thinks he's a Magnificent Bastard (for in-universe reasons)" as the final call on what makes a MB different in a cast of Chessmasters playing a Thirty Xanatos Pileup (A Song Of Ice And Fire is a good example) is generally out of universe. Remember, it's the audience reaction that makes the character type - either a Worthy Opponent, or a Love To Hate villain depending on the author's intent to have the character received as such.

IOW, too many people seem to think Smug Snake is the Counter Trope to Magnificent Bastard, when a better diametric opposite would be the Antivillain or Jerkass Woobie (intentionally written to be sympathetic) as sometimes the audience could all too easily paint a Smug Snake as a Magnificent Bastard. Better Counter Tropes to MB would be Harmless Villain or Minion With An F In Evil.

Regardless, a story where a MB villain wins could be a Deconstruction or a Bittersweet Ending, but a victory for a Smug Snake is a sure sign of a Crapsack World.

No. He's upfront about how slimy he is, hides his arrogance poorly from anyone who isn't a dunce (see: Sultan of Agrabah) and relies on mind control even for that. Seriously, when you need mind control to make the Sultan do what you want to, you're a failure as an Evil Chancellor, let alone an MB.

Again - the MB is meant to be, if not necessarily respected, then feared. The Smug Snake is meant to just be outright hated. Machiavelli advised the former while warning strongly against the latter.