Generally under "really bad autism" is not meant as part of the spectrum of conditions, but a very narrow behavioral problem that parents have to deal with. The difference between what makes autistic person a "really bad autism" also differs for various social situations, so let's not go there...
> a very narrow behavioral problem that parents have to deal with
Let's not define autism in relation to what other people have to deal with. For years, autism has been discussed not in terms of what the autistic person experiences but what the people around them experience. That's kind of BS. Someone else being autistic isn't about you, it's about them.
You're welcome to talk about people with "high support needs", or people who have certain struggles in social situations, but discussing "really bad autism" just reinforces that negative stigma that autistic people shouldn't be thought of as people but rather as problems that "normal" people have to deal with.
