The Seventh Doctor displayed perhaps the most profound change in attitude of any of the Time Lord's personae, beginning as perhaps the most outwardly amiable and bumbling (to the extent of putting himself in danger but not at the cost of his overall great intelligence and benevolent intentions) and progressing into a driven, dark gamemaster whose plans to defeat his adversaries, both old and new, would play out across space and time. He generally displayed an affable, curious, knowledgeable, easygoing, excitable and charming air. However, as he began to choose his battles and keep a tighter grip on his secrets - from his plans to his very identity - he also presented more serious, contemplative, secretive, wistful and manipulative sides with undercurrents of mischief and authority, constantly giving the impression that there was more to him than met the eye.
As something of a showman, the Doctor would sometimes act like a buffoon, usually preferring to manipulate events from behind the scenes; much like his second incarnation, he was prepared to play the fool in order to trick his foes into underestimating him, inevitably leading to their defeat at his hands. He was an adept physical performer and once deployed a repertoire of magic tricks, illusions and escape artistry to this effect as part of his plans. Although his more obvious whimsical tendencies disappeared over time (particularly his spoons-playing), he maintained a fondness for idiosyncratic speeches that occasionally referred to literature, ordinary places and even food and drink amidst the weightier concerns on his mind. He was empathetic to his friends (and even his enemies, such as Helen A) and somewhat melancholic at times (such as during Mel's departure and before his decision to eradicate the Daleks) but now placed greater burdens upon himself in the name of protecting the universe. This may have led him to surround his true intentions in mystery and the use of sleight of hand as befit his fondness for performance, in effect, subverting his more lighthearted qualities to complement and enhance his heroic and darker ones.
Given the Seventh Doctor's appearance and stature, he was surprisingly capable of both directly and indirectly taking control of situations involving strangers, using his greater intelligence to assess and direct events. Concerned with the bigger picture, he would sometimes overlook the finer details and his planning, both pre-prepared and improvised, would sometimes have fatal results and consequences. When he acted to end threats, it was usually a ruthless, destructive and final manoeuvre. He was also not above hiding the truth from his friends and allies and using them in order to complete his schemes and gambits.
In direct contrast to his third incarnation, this Doctor was absolutely opposed to violence of any sort and he was totally against the use of firearms, although he also proved capable of rendering a man unconscious with a touch. In keeping with his established habits, he would use gadgetry of his own invention when the situation called for it, but never as his final gambit. Instead, he almost always managed to talk his enemies into submission, often into suicide.
It is indeed fitting that this, at times one of the darkest Doctors of all, should not directly use physical force to implement his actions, even though he seemed to have the universe's weight on his shoulders more often than any other Doctor.