Well obviously you've already done your trials, but I'm bored so I thought I'd answer anyway. Please note that these are totally off the top of my head.
Moral decay in The Big Sleep:
Eddie Mars directs his hitmen to threaten, beat up and even kill people to protect his own interests. He is a "killer by remote control", prefers to pay others to do his dirty work. He appears to lack a conscience and any sense of morals.
Agnes Lozelle (sp?) exploits and manipulates those around her so that she can attempt to gain power and wealth. She attaches herself to a series of men e.g. Joe Brody, Harry Jones, then abandons them when the going gets tough. She pretends to love Harry and claims that she wants to marry him. Yet Marlowe sees through her deception and realises how little she cared for Harry after he is killed.
Carmen's nymphomania and insatiable sexual appetite is another example of moral decay. She throws herself at all men and tries to charm them by acting coy and innocent. Her frustation is so strong that when Sean Reagan rejects her advances, she murders him.
Arthur Gwynn Geiger and Carol Lundgren's understated homosexual relationship.
Widespread corruption in society, people indulging in vices e.g. pornography (A.G. Geiger's lending library of smut), drugs (Carmen's drug use) and gambling (Eddie Mars' gambling den).
Moral decay in The Skull Beneath The Skin:
Ambrose Gorringe is very obsessed with Courcy Island, so much so that he is prepared to kill people e.g. Simon and Cordelia to keep it in his possession.
Clarissa and Ivo Whittingham's affair.
Clarissa is extremely self-centred and constantly hurts others with her cruel comments and behaviour.
Hope this is helpful for someone!
