Relationship friction, failures and mistakes, power struggles, ego-related conflict

Being gaslighted by someone who makes the character question what they know to be true
An undercover cop infiltrating the character's circle of friends to gain information 
A love interest feigning romantic feelings for the character to gain access to their friend
A character being kidnapped and falling victim to Stockholm Syndrome, developing sympathetic feelings toward their captor 
The character being blackmailed with proof they engaged in unethical behavior
A cult or governmental regime using propaganda to brainwash the character 
The character's children using guilt to convince him or her to do what they want
An organized crime boss threatening to harm the character's loved ones if they fail to follow certain orders
Being scammed or phished by a con artist
A rival preying on the character's weakness to sow self-doubt
A parent using guilt or coercion to get a child to behave
Being deceived by a love interest who only allows the character to see what he or she wants them to see
Being catfished by a suitor who wishes to gain access to the character's wealth
A manipulator telling the character half-truths or innuendo so they form incorrect conclusions 

The character being coerced into doing something minor they normally wouldn't have done (telling a lie, covering for a co-worker, etc.)
Awkwardness and anxiety from having to confront the manipulator
A manipulated victim developing romantic feelings for their abuser and entering into a relationship
The character being blackmailed and having to lie so loved ones won't find out
The character being embarrassed that they were taken in
Friction arising when a character in denial is confronted by loved ones about the manipulator
Resulting inconveniences from cutting ties with the manipulator (having to find a new accountant, losing a carpool associate and having to drive the kids to school every day, etc.)