Dangerous
Normally, conscious reaction functioned like so;
Perception -> Processing -> Decision making -> Reaction.
But Hever's mastery of Meteor Swing functioned like so;
Perception -> Muscle memory -> Reaction.
Of course, this was extremely difficult to accomplish. It took a long time to build such immense amount of muscle memory. Merely general mastery of a technique was not enough.
This was the fruit of five continuous unhalted rigorous years of training with the Meteor Swing technique. The Meteor Swing was a counter-offensive technique, it was meant to be used when the user was attacked.
By practicing the Meteor Swing over and over and over against countless kinds of attacks, he had burned those motions into his muscle memory.