When someone has this bad trait, everything they say or do is aimed at making them appear good, becoming the center of attention, or showing to the world that they are deserving of special treatment.
They feel they are just fated to be stuck and unhappy, that the universe is against them, that life is a terrible joke, or that the game is rigged against them.
They have a primal desire to prove others incorrect, and if they are unable to do so, they will resort to various tactics to discredit people with whom they disagree.
They will extract whatever they can from you, regardless of what you want or need. And they're voracious. They always want more, no matter how much you offer them.
No offer of assistance (financial nor otherwise) comes without hooks attached or without some ulterior goal in which you and your interests are only minor actors.
If you spend enough time around other people, you'll eventually encounter someone who is quick to criticize others based on what they see — even if they don't know the complete story.
The manipulative individual utilizes other people to achieve their goals. They frequently take pride in their ability to influence people.
They don't apologize — at least not honestly — because whatever they did to harm you was your fault. You incited them.
They become obsessed with making you regret ever going against them in any manner - even if "going against them" just means ignoring them, disagreeing with them, or refusing to do what they want.