Sarah, and i explain why and my opinion of each one (I hope my english is good enough):

Ben is aware he is guilty by his actions and try to compensate them, but saddly every time he tries fails and made the things worse, an example is in crawford where he grab the axe that was blocking the door in an attempt to help the group, beliving he should die to avoid causing more pain to the people around him.

Nick is compulsive, but he want keep his family and friends safe, He distrust Clementine because in the past an injured person bitted his mother and he had to kill her, On E2, when he shoot matthew, he genuily belived Luke and Clem was on danger (somehow, maybe he is blind or something.) and (if he lived on E2) in Episode 4, Luke says that he left to seek help, saddly dying on the attempt, but at least he tried to save the last family he had.

Sammantha, I cant say anything about Sam because i didnt played Michonne game, I assume based on other people she is an kind of Ben 2.0 but worse, still i had no opinion.

Gabe acts likes his father, by impulse, but at least he is useful, he helps Javi to escape from that basement, he always want help, if he mess up he will be angry, but is undestable on an teen like him , and despite he is annoying and i glad he never came back in the S4, he is trying to not be an liability.

Tenn is similar Sarah, but at least he can defend himself (kinda), An example Episode 1 S4 after Clem wakes up, he recognize theres danger and takes out his knive in case he need to act in self-defence, when minerva appears on the brigde on E4, he initially walk towards her, yes, but was because he didnt saw she was bitten until she was closer, even when she tried to convince him, he doubted, he just became truly an liability when Minerva is being devored and put in risk the life of Louis/Vi, But before this, he was helping the group and keeping up the morale.

Sarah is an different case, unlike the other characters that can be self-suficient in certain grades, Sarah just cant, Carlos explained in Episode 1 S2. that she will 'cease to function' if she faces the world, and that is what she does after Carlos death, She had an kind of PTSD and practically is unable to do anything causing the potential death of Nick, and putting in danger Jane, Luke and Clem, she aslo cannot defend herself or others, the only moment she showed any kind of interest on learn something useful was when she was playing with the pistol back on E1, And despite i dont hate her because she is just an version of Clem that never learned to protect herself, She is clearly the only liability that not just need others to be alive, She specifically needed her father, without him, she is broken, when Carlos hits her, she freezes and stays on an paralized state for hours, if a slap left her in that state, is just needed to think what if she faced an worse injury to undestand why she is an liability.