Shirayuki Berii/Mew Berry (a.k.a. "Berry Sue") from Tokyo Mew Mew a la mode. This is an especially grating case, because the translators made the fandom wait forever for a sequel, only to release it... and reveal that Ichigo and company had been reduced to living accessories for an unsympathetic ditz who immediately gets twice the power of any previous character (for no reason at all, Ichigo's powers can now only be sustained for enough time to give Berii a power boost, at which point she turns into her helpless kitten form), magnetizes the cast so that they immediately start stalking her to see how special she is and transfer to her school for no good reason, and makes everyone love her more than their sanity. While she's also a God Mode Sue, it's not so much her ridiculous power level that's offensive as how she derailed the rest of the cast into a fawning fan club.
Bella Swan of Twilight. She's clumsy, whiny, unattractive, rude, vain, has no self-esteem, and no sense of humour. Yet two sexy supernatural boys fall head over heels in love with her (one of which is willing to buy/give her everything her little heart desires), the boys at school want to date her and the girls wants to be her friend, the Cullens immediately accept her as a part of the family—everyone aims to please her, pretty much. Then in the fourth book, after her transformation into a vampire, she turns into a full-blown Mary Sue. A beautiful, powerful, sparkling Sue.
