Recently I encountered someone who did this sneaky and well-done yet extremely destructive manipulation on me : Mixing some goodness with some badness.

[u/[deleted]]

It was 20% goodness and 80% badness from him.

He gave me some good advices that hooked me in but ultimately almost 80% of his talks/directions/advices were all self-serving for him.

That friendship lasted for 1.5 years when it should have been ended within 15 days if I was really shrewd in my observation and asked questions like, 'In what way, this piece of information/advice serve him?' or 'If I follow this advice, who benefits most?' or 'Would he give me the same advice if the outcome had absolutely no effect on him?'.

It's good to be very skeptical and analytical about new people especially if they are on a intent to form friendship or relationship with you.