2. Emotionally Abusing Ace
The Doctor has been something of a teacher from time to time, helping his companions to grow and better themselves. Generally, they are aware of what's happening, even if they don't entirely enjoy the experience. When it came to the Seventh Doctor's treatment of Ace, however, it went a little further than audiences were used to.
Ace had burned down Gabriel Chase, an old haunted mansion, as a teenager due to an evil presence that she felt there. This fear had stayed with her through her life so the Doctor secretly brings her to the house, one hundred years before the arson attack. He doesn't tell her what he is doing, opting instead for a slow reveal that Ace is infuriated by.
As this house had featured in much of her trauma as a child, to find that the Doctor almost casually brought her there deeply disturbed her. The Doctor shows little to no remorse for his actions either, even when his intended outcome doesn't come to pass. When the danger is over, he asks her if she has changed how she felt about the house. She coldly answers that she now wishes she had blown the house up, rather than burn it down.