These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Base Breaker: Avenger-Fans have largely forgiven her for her actions during Disassembled/House of M, mainly because it was established in The Children's Crusade that she was not herself at that time. On the other hand, for most parts of the X-Fandom she is still The Scrappy, because she never got any real punishment while Cyclops (whose actions also happened under a mental breakdown and possession) gets him hunted down like a criminal.
Designated Hero: X-Fans staunchly view her as this. Wanda continues to get pushed as a heroic figure, particularly in the aftermath of AvX. However when she was killed by Rogue during Uncanny Avengers in retribution for what effectively amounted to genocide for her part in Decimation, X-Fans cheered.
The Avengers 111, 1973. Magneto had captured the X-Men and several Avengers, turning them into People Puppets. Only 3 Avengers were still free, Thor, Vision and Black Panther. So sure about his strenght in numbers over the Avengers, and with the Scarlet Witch dancing under his control, he said "But they are decimated, Piper - DECIMATED!"◊ (bolded in the original). He would surely come to regret those words: in House of M the Scarlet Witch, mad and with reality warping powers, turned all mutants except 192 into normal people without powers, including Magneto. The name of the near-extinction of mutants? "Decimation".
Avengers Forever mentions that Immortus was afraid that Wanda or her sons would become insanely powerful and change reality itself; and manipulated her and the Vision to get married so that she did not have any sons. Many years later, in Avengers Disassembled and House of M, Wanda becames the force that Immortus feared. And even more years later, in The Children's Crusade, she does have a son with similar reality warping powers...
The popularity of those two storylines, along with her absence from the comics between 2005 and 2011, means that it's common for readers to think of her as an omnipotent Reality Warper, even though her powers don't work that way anywhere except Disassembled and House of M, and both those stories have since been explained away as the result of an outside source amping up her powers.
The Woobie: While she's done some questionable things, it's pretty hard not to feel bad for her.