Like many protagonists, the Doctor – over the last fifty-seven years – has defined themselves by rules and limits. Adopting, where possible, the Time Lord philosophy of non-interference, as well as his own moral codes of helping those in need and avoiding doing harm to others. The Doctor, usually, is simply a traveller in time and space, just “passing through”.
Even after at least fifteen incarnations, there has always been a great deal of similar qualities passed down throughout the years. Granted every Doctor brings something new to the table, but inside, they’re still the same individual through and through.
But sometimes, the Doctor isn’t very ‘Doctory’, doing something which seems slightly out of character, and without reason. This could include moments such as the Time Lord Victorious moments in The Waters of Mars, however, there is justification for these actions, as well as realisation from the Doctor that he’s gone too far.
But sometimes these out of character moments come with very little reasoning or are just unjustifiable, with the Doctor showing very understanding in their actions.
Whilst these moments don’t necessarily ruin the show - if anything some enhance their episodes - they’re still very out of character for our titular Time Lord.