People always say that there is drama in conflict but what can be forgotten is that stability is needed too. As much you need to build the conflict in your character still needs something solid and reliable whether it’s a hobby, a place or a person. In many, though not all, stories it falls to a person; the detective often has their trusty sidekick, the romantic hero/heroine their best friend and confidant, the spy their old ally/adversary.
They can be the way the character communicates feelings/thoughts to the reader, their moral compass, or a proxy for the reader. Whatever function these character’s serve they often have a complex emotional relationship with the protagonist. A regular one is the detective’s sidekick who is both frustrated by and admires the protagonist while, often but not always, providing the emotional stability or normality the detective lacks. Morse and Lewis in the Morse books by Colin Dexter, Dresden and Murphy in the Dresden Files by Jim Butcher, and, of course, Holmes and Watson. As a trope it appears again and again partly because the maverick often needs someone to give them a kick up the backside when, or before, they go too far but also because the character needs an anchor in the storm that is the story.
In the case of Watson not only does he ask questions on behalf of the reader and act as a figure for Holmes to explain things to but he also balances Holmes’ logic. Where Holmes is all logic and calculation, Watson is emotion and humanity. This is not to say that as a character Holmes is inhuman but he can be dismissive of people in a way that Watson isn’t.
In the Morse stories Lewis provides a similar support for Morse and more than once Lewis solves the case through observations that Morse fails to make because he is too bound up in the intellectual world. Morse approaches cases like a crossword puzzle, whereas Lewis approaches them on a more emotional level. Unlike Holmes Morse certainly has a complex emotional life but like Holmes his life is his work whereas Lewis, like Watson, has a more balanced life, work is important but Lewis also has a family outside of work, just as Watson marries.
In the case of Dresden and Murphy it’s slightly different because Dresden is a wizard and a private detective so Murphy, a police detective, provides a link to the human world. Their different approaches lead them to butt heads but they are friends and their aims often intersect as they both work cases from their differing angles. Perhaps in this respect they are also slightly different because although Murphy needs Dresden’s advice about magic when it comes to the detecting stakes they are both equals whereas the sidekick is often portrayed as good but not quite as good as the maverick who is exceptional.
So, be as cruel as you want to your character but do give them a drinking buddy or a safe place so they can relax a moment before hurtling off into their next adventure.