If Hee Ryang clears Yeonjo's father's name and frees him from slavery then I might see a c...

Impossible. Heeryang kill all HIS family, kidnapping and rape him for mouths i don't see the redption

Well...
Hee Ryang has done terrible things but he didn’t kill All of Yeonjo's family .He spared Yeonjo and his older brother's lives.He wasn't hungry for blood .He was doing his part to eliminatine young king's main supporters. And by doing so he saved many people in the border of his country .

For other things he has done to Yeonjo , yes he deserves to rot in hell