Anvilicious, Author Tract - High Society drops anvils advocating the legalisation of drugs and criticising the power wielded by sensational tabloid media. The other books are also prone to this, but less so.
Complete Monster - Geraldine in Dead Famous, Captain Shannon in The First Casualty. Dick Crosby in Past Mortem has a Freudian Excuse (it's implied that he was driven insane by the bullying he suffered at school), but his actions alone qualify him for this trope.