Scarlet Witch is a force to be reckoned with. While other Marvel characters such as Captain America and Iron Man are considered the heaviest hitters due to their movies, the truth is that Wanda Maximoff is arguably the most powerful being in the Marvel Universe. The number of crazy things Scarlet Witch has done in the comics transcends beyond hero or villain, putting her into a near-god category.
Scarlet Witch often uses her reality-bending abilities to bring order among the chaos. However, many Scarlet Witch plotlines in the comics showcase how dangerous she can be. Then there are the plotlines which she's just crazy in general. Here is a taste of some of craziest, most batsh*t things Scarlet Witch has done in Marvel comics.
Three simple words changed the entire Marvel Universe. In 2008's House of M story arc, Scarlet Witch simply uttered "no more mutants" and nearly the entire world's population of mutants vanished. Aside from a couple hundred X-folks, all the mutants on Earth were de-powered. It's the first time a genocide occurred without any mass deaths being involved.
Okay, this is gonna be a little messy. Since robots and humans can't bear children the old-fashioned way, Scarlet Witch used magic to conceive her twin boys, Thomas and William, but it turned out that the twins' souls were actually shards of the demon Mephisto. Wanda did give birth to them, but Mephisto absorbed the boys back into his being, leaving her emotionally crushed. Wanda's mentor, Agatha Harkness, removed Wanda's memories of her children from her mind in order to protect her. These events would eventually lead to the chaotic event that nearly ended the Avengers. Also, it turns out that the souls of the two boys were reincarnated into the Young Avengers Wiccan and Speed. That's comics, people. Comics.
Times were desperate in Avengers vs. X-Men, when the Phoenix Force contained five of the most powerful mutants on the planet. In order to stop the cosmic Phoenix, Scarlet Witch teamed up with the possible savior mutant Hope to take out the unbalanced entity that empowered the already powerful Namor, Magik, Colossus, Emma Frost, and Cyclops. Think of how powerful Wanda must be if she could take out the Phoenix, an entity so powerful that it eradicates entire planets.
Things stop making sense in the Marvel Universe and start getting deadly in Avengers: Disassembled. Jack of Hearts, the Vision, Scott Lang, and Hawkeye are killed in various odd circumstances. She-Hulk goes crazy, Iron Man appears drunk despite being sober, and all kinds of nuttiness is tearing the Avengers apart. It's revealed that all of this chaos is due to the unhinged Scarlet Witch constantly changing reality to dismantle the Avengers. While she was ultimately subdued, her plan worked. She successfully broke up "Earth's Mightiest Heroes"... well, temporarily.