O'Brien, in chapter 2 of Book 3, takes very special care of Winston while torturing him. This is a little ironic since the purpose of torture is pain. O'Brien shows significant restraint and care for Winston in his words. Look at his considerate language:
'I am taking trouble with you, Winston,' he said, 'because you are worth trouble. You know perfectly well what is the matter with you. You have known it for years, though you have fought against the knowledge. You are mentally deranged. You suffer from a defective memory. You are unable to remember real events and you persuade yourself that you remember other events which never happened. Fortunately it is curable. You have never cured yourself of it, because you did not choose to. There was a small effort of the will that you were not ready to make.
These statements show a somewhat forgiving nature in O'Brien. O'Brien wouldn't forgive Winston if he did not have love for him. In fact in narration, Orwell described O'Brien's nature specifically like this:
When he spoke his voice was gentle and patient. He had the air of a doctor, a teacher, even a priest, anxious to explain and persuade rather than to punish.
These words demonstrate a genuine character. All these occupations are jobs that require love and attention to those with whom the people serve.