To reach maximum personality ranking, you must pick one moral choice and STICK with it for all the cases in the game. If you Absolve the criminal in the first case, you need to Absolve/Arrest every criminal in the following cases, otherwise you will need to replay the whole case again to do it.
In Case 2 - The Train Case, the options will be "Blind Justice" and "Political Game". Blind Justice relates to the Condemn option and Political Game relates to Absolve.
In Case 4 - The Abbey Grange Affair, one of your conclusions can reach the options of "Glory to Lestrade" and "Trump the Police". I am not sure if these conclusions will help reach maximum personality rank as you are not catching any criminals (because this conclusion is so very very wrong)
In Case 5 - The Kew Gardens Drama, if you select "There is no Accomplice" as your conclusion you will not change your personality ranking as again this conclusion doesn't lead to you catching any criminals (and is again, wrong)