Were any MAJOR sex traffickers or sex slave operations ever busted?

Yes, plenty of sex trafficking operations have been shut down. Immigration and Customs Enforcement is one of the agencies that does this, and it has arrested hundreds of people.

A lot of it, though, isn't the sort of thing you see on movies like "Taken" and so forth, and often the groups involved are not as big as you might think, or they may be involved in other crimes as well. Groups that moved more than 1000 people at once would likely be quite rare.

In most cases, they don't kidnap or abduct people, as doing so tends to attract attention and is the sort of thing that gets reported. More commonly they do things like offer people jobs or visas, for a fee, and when the victims arrive, their passports are confiscated and they are told they have to work to pay off a supposed debt to the traffickers. Many are often scared to contact the police, as they have been told they could themselves be arrested.

Even if they are, bureaucracy either prevents a sentence or makes it lenient.

I think they should face capital punishment.

Define 'major', please.