Upvote:2
The "Intimidator" is the tallest, fastest, and longest coaster in the southeast. It's located in the Carowinds Plaza near Charlotte. They seem to have a massive number of "Thrill rides". It is a bit far away (3+ hours drive) but might be worth for a day trip.
Other parks closer to Myrtle beach are the Hard Rock Park, which looks a lot tamer, the Family Kingdom, which offers a lot of kid-friendly rides but also one wooden roller coaster.