When he meets Marta, he and the cops visibly doubt her claim that lying makes her vomit, and puts it to the test by baiting her to lie. She does, and... she does. He immediately apologizes, and obviously genuinely feels bad about it.
Blanc: Dear girl, I'm sorry! I assumed you were speaking figuratively.
When he sits down by Nana and offers sincere condolences to her, recognizing that nobody else in the family had.
While Blanc openly tells Nana that he's there to question her for information, he also makes a point of telling her that she shouldn't feel pressured into telling him straight away, because he's perfectly willing to sit a while and enjoy her company. One suspects that it's been a while since Nana has heard that particular sentiment.
Telling Marta she didn't kill Harlan because she knew what she was doing "Because you're a good nurse." For a character who is as much of a Woobie as Marta, even that simple recognition means a lot.
After being comically aloof for the whole film, upon figuring out the full depths of Ransom's scheme he's absolutely furious as he delivers The Summation, laying into Ransom for what he and the rest of the family had put Marta through for years.
Harlan expressly tells Marta during his plan to give her an alibi that the dogs like her, so they won't bark. Indeed, they come to her for cuddles and she takes the time to pet them. In a Freeze-Frame Bonus, you can see one of the dogs looking worried when Marta nearly falls off the trellis. (This explains how the dog ended up with the piece of wood it later gave to Marta and later Benoit.)
Despite being just as horrible and vicious as the rest of her family, Harlan's eldest daughter Linda revealing to Walt that she does actually mourn her father's death, seemingly the only one of his descendants who does miss him and isn't just preoccupied with who gets what in the will.
At the beginning of the scene, Linda is shown weeping in her bedroom, and Walt walks in and gently asks if she is alright. It's a lovely, understated moment of affection between the siblings, and at the end of the scene, the two share a hug.
In addition to the above, Linda is also shown to adore her father's dogs, greeting them with a joyful "Hello, puppy!" when they come running to her, and petting one during Marta's attempted confession.
Meta example: Chris Evans, a known dog-lover, really got along with the two German shepherds off-camera. Someone even joked that Evans' best acting isn't being Ransom, it's pretending he doesn't love dogs.
Similarly, despite Blanc's cynical nature, he states that one thing he's found to be true is that dogs are an excellent judge of character. This is said while smiling fondly at Harlan's dogs, who he pets and plays fetch with multiple times throughout the film.
In the final scene, after everything she's gone through, Marta looks at Harlan's portrait. Despite wearing a grim expression throughout the film, he now looks at her with a kind, proud smile.
Though we don't see much of the Cabrera family they are, hands down, far more stable than the Thrombeys.
As early as the movie's second scene Marta's mother is trying to be aware of her daughter's sensitivities in the wake of Harlan's death by asking Marta's sister to turn off the murder mystery she was watching. While Marta's sister gets a bit snappy with her mother over the subject, she is sincerely apologetic to Marta herself about it.
Then there's nothing but warm interactions between Marta and her mother when she comes home that night.
Marta's relationship with Harlan - from the brief moments we see the warmth and playfulness between them makes it clear how close the two of them were. It's even more clearly established to be genuine affection when Marta even calls him "abuelo" during their last Go session, and "abuelo" is Spanish for "grandfather." Even if the other Thrombeys never really accepted her, it's clear from that alone that Marta was and always had been part of Harlan's family, whether the rest of the Thrombeys chose to accept it or not.
And while his death may have turned out to be a Senseless Sacrifice, he cared enough about Marta that he chose to literally give his life for her, and to do what he could to salvage her situation and keep her undocumented-immigrant mother off the legal radar. It's telling that when she first informs him that she has just committed an Accidental Murder on him, he never gets fearful or angry (either or both would be quite justified); instead, he Faces Death with Dignity and spends his last minutes looking out for her.
Furthermore, when Marta's mother is telling her sister to turn off the violent crime show she's watching, she describes Harlan as "a friend Marta loved very much", rather than a boss, which indicates how fond Marta was of him.
Meg seems to be the only Thrombey other than Harlan to genuinely care about Marta. While several of the other Thrombreys simply claim to view Marta in high regards, Meg actually shows it, from greeting her like a sister, getting angered when police tried to stop Marta from entering the house and referred to her as "the help," comforting Marta alongside Fran when they believe Marta needs it, and later on, tries to convince Joni that Marta should get the inheritance like what Harlan wanted. True, she later ends up telling the others about Marta's family's illegal immigrant status, but she could easily have been gang-pressed into that. (Though it should be noted that Meg's character is ambiguous, and that it can be questioned whether Meg is sincere in her affection towards Marta or whether she is just putting on airs.)
Marta also tells Meg that she'll pay for the rest of her time at Smith College - we never hear that being recanted, so there's a good chance it will happen.
After Harlans will is read and the family starts freaking out, Linda starts yelling at Marta and corners her. Meg, seeing this, immediately runs to help hold Linda back, and after Linda accuses Marta of boinking Harlan, Meg instantly takes offense and in the background of the commotion can be seen defending Marta and arguing with Linda about it.
Trooper Wagner is just so obviously but respectfully giddy that you can't help but feel good for him being involved in what seems exactly like the kind of case that drew him into policework.
Meta-heartwarming: he is played by Noah Segan, who had previous played one of the antagonists in Brick and Looper. Considering the fact that both films were by the same director, it's genuinely nice to see him play a character who isn't a villain and a Butt-Monkey.
Lieutenant Elliott and Benoit have a pretty wholesome working relationship. The former trusts him and affectionately calls him "Benny". The detective may be quirky, but he's also in the field for a reason.
When Lee of Cinema Wins did his video on the movie, he was curious about one particular character's job, so he took to Twitter to ask the actress about it. Rian Johnson did him one better and answered the question himself, to Lee's delight.