What is the hardest standing tumbling?

Answer 1

a standing full

^that is one of the hardest skills. the actual hardest is a standing double, normally performed in All-Star Cheerleading.

^the hardest standing tumbling is actually a standing double layout commonly used in college or competetive chherleading.

Answer 2

Any gymnast skill is hard. They all take a lot of practice & training. I'd say the hardest to learn at first is a full.