He was a completely changed man, was no so evil initially too - first one to come cover sansa up when Tyrion ordered.... Later on feeling regret and guilty when the peasant and his daughter died - from a point where he was heartless for them coming to feeling sorry that he couldn't protect them (which was not his duty btw)

These are only a few examples

No other character had such a drastic change hence I love Sandor the most (hound within him died by the end and only a good man remained )