Hermione cast the Imperius curse on Ron from behind and had him drink three vials of very strong lust potion. He really deserved to die in pain after going to Azkaban and upsetting her boys. However, this was serving a purpose. He was mounting her double before she could even blink once she allowed him to. She even dropped the Imperius, no point in wasting the magical energy. He couldn’t stop shagging if he wanted to. He was so loaded with potions.